USRSA Certification Program

Supplemental Study Guide 2009-2010

Introduction

USRSA Supplemental Study Guide 2004

The USRSA initiated the original stringer Certification program in 1986 to recognize individuals with a basic level of stringing competence. Today's Master Racquet Technician (MRT) program recognizes and rewards racquet sports service professionals who demonstrate superior technical competence and product knowledge.

The USRSA and the industry will support MRTs' competence and expertise by actively encouraging players to seek out MRTs for racquet sales and service.

Racquet technicians who pass all portions of the certification exam will receive a "Master Racquet Technician" certificate. It is the intention of the USRSA that this certificate be considered by:

Certification by the USRSA, whether as a Master Racquet Technician, or as a Certified Stringer, involves a comprehensive written test and a detailed practical test. Each measures your understanding and skills with respect to all facets of racquet service — installing grommets and string, re-gripping, and handle sizing. Additionally, to attain MRT status, you'll be required to demonstrate understanding and customization of weight and balance as well as current frame and string technologies and how those technologies translate to player satisfaction.

USRSA Certification Programs will:

The primary source of material for certification is the USRSA's Stringer's Digest, which is sent to each member. The information in this Supplemental Study Guide is best understood in conjunction with the information presented in the Stringer's Digest.

Requirements

MRT status will be good for one full year from testing date. Maintaining MRT status will require passing an annual written mini-test designed to demonstrate understanding of the year's significant new technologies. This mini-test will be open book, and will be administered through the mail.

Certified Stringer status will carry no expiration date.

Applicants will take a three-part test: a written (multiple choice and short answer) section, a racquet evaluation section, and a hands-on racquet service section. Applicant is allowed to use a Stringer's Digest or manufacturer's instructions during the stringing section only.

Applicant will supply a strung racquet. Racquet must be less than three years old and in good condition. The applicant will also supply a new replacement bumper and grommet system for this racquet.

All applicants will cut strings and remove bumper/grommets from a racquet. Applicants will then install new bumper/grommets and string the frame under the observation of the appointed USRSA tester.

Professional machines will be supplied at each test site. Applicants may bring a machine of their choice with USRSA approval. If you have any questions or problems regarding machine use, contact the USRSA. Basic tools and accessories will be available at the test site; however, applicants are encouraged to bring their own tools.

Applicants will string a racquet installing a synthetic string in the mains and natural gut in the crosses. Applicants will be given approximately 19'6" of synthetic string and approximately 20' of gut and should be sure to bring a frame which accommodates these string lengths. The frame must also accommodate two lengths of string (with 4 tie-off holes). Applicants upgrading from Certified Stringer to MRT will not be required to take the hands-on portion.

All applicants will increase the handle size of their racquet by 1/8 inch using a provided heat-shrink sleeve. A heat gut will also be provided for shrinking the sleeve. Applicants must also apply a synthetic replacement grip to a racquet. Grips provided will include a self-adhesive backing, eliminating the need for two-sided tape. Staple guns are provided for securing the grip to the butt cap. This is a required procedure for the test.

Grading

Applicants must: A) score 84% or higher on the written portion; B) correctly answer 84% of the questions posed on the racquet evaluation section; C) achieve an evaluative score of 14 (out of 17 possible points) on the string/grommet removal and grommet replacement section; D) achieve an evaluative score of 84% on the stringing section and; E) execute building up and gripping a handle without any errors. In addition, the stringing score sheet contains 8 criteria which must be met to achieve a passing score, regardless of the point total. These include: alternating tensioning of mains (no more than 3 strings ahead on one side), pulling one string at a time, avoiding notching of mains during weaving, installing pattern specified by manufacturer, avoiding crossovers at the head, avoiding any mis-weaves in string face, turning in a frame without cracks or broken/cracked/unseated grommets, completing the bumper/grommet removal and replacement within 20 minutes, completing the string job within 60 minutes, and completing the handle sizing/grip replacement within 20 minutes.

Hands-on procedure

Applicant understands the proper use of a balance board and placement of lead tape.

Applicant displays proper string cutting & bumper/grommet replacement techniques.

Applicant displays proper stringing techniques.

Applicant displays proper handle sizing and gripping techniques.

Customer Service

Racquet Selection

(MRT applicants only)

No one racquet is for everybody. In determining the needs and wants of a player, you'll need to gather as much information as possible. Whether fitting a tennis, racquetball, squash or badminton racquet, there are key questions you'll want to ask your customer to ensure he is satisfied and enthusiastic about the racquet you've sold him. Remember, the best advertising is word-of-mouth. It's also the least expensive! Among the questions you'll want to ask are, why are you changing racquets? What racquet do you currently use? What do you like and dislike about it? Do you prefer a midsize or oversize racquet? How much would you like to spend? You'll also want to know how many times per week he plays, his playing level and playing type, whether he has any arm or shoulder injury problems, if he's looking for more power or control, if he has loyalty to one particular brand and what court surface (tennis) he plays on. After you've narrowed the choices to 2-3 racquets, encourage the customer to take out a demo for a few days. Perhaps even offer two different racquets so he can compare their performance and feel. Be sure those demos have good quality strings and grips too! If a customer brings you several racquets and asks you to make them all feel the same, you can adjust racquet weight and racquet balance, but you cannot adjust racquet stiffness.

String Selection

When recommending strings, take the same approach as if you were selling a racquet. Too often, 30 minutes or more are spent on the racquet sale and the strings are selected on the basis of color or price. Remember, the racquet sale earns you a one-time profit, whereas stringing profits are (or should be) repetitive. Take the time needed to fit your customer with the right string and the right tension. Whether you're stringing a newly sold racquet or someone's favorite old-timer, the right string and tension can determine how that racquet plays. Having a checklist will ensure consistency in how players are being serviced.

Many of the same questions asked to select a racquet will help fit the player with the right string and tension. Be careful not to slip into the "same string, same tension" mentality for regular customers either. Let them know about new strings in your inventory. Keeping accurate records will assist in determining whether a player is restringing often enough. It can also provide information on tensions, grommet replacement, grip replacement and any special needs.

You can service a player with a sore arm by: lowering tension, using a "softer" or multifilament string or natural gut, using a thinner string, checking and possibly altering grip size, adding a softer grip, possibly adding weight to the frame (to dissipate shock) and finally, encourage them to restring often enough. Many players pride themselves on not restringing for a year or more, believing the only time to restring is when a string breaks! Inform your customers about strings losing their resilience, requiring they do more work with their arm. Most are only aware of strings losing tension over time (which can lead to a loss of control), but explaining the loss of performance will provide further incentive for a player to restring.

String Technology

The term "synthetic gut" no longer carries much meaning. It does not mean that a string has a specific construction or playability characteristics like natural gut. It simply means the string is made of synthetic fibers. Most synthetic strings are constructed of nylon in a variety of ways to modify playability and durability. Some claim to duplicate natural gut's resilience (providing maximum power and feel) at a fraction of the cost. Synthetic strings tend to be easier to install than natural gut. When stringing with natural gut, it's important to avoid kinking the string as this could cause premature breakage. Typically, elasticity will govern a string's ability to return energy to the ball. Elongation is the measure of a string's elasticity and is closely related to the power potential of a string. It also is a measure of a string's ability to absorb incoming ball shock during impact. All things being equal, the greater a string's elongation, the greater its ability to absorb incoming ball shock. Generally, multifilament strings with no center core have the greatest elongation of nylon strings. As a result of this characteristic, some multifilament strings lose tension faster than center core constructed strings. Pre-stretching can reduce short term tension loss or "creep" and some manufacturers recommend pre-stretching for this reason. It also helps reduce the string's tendency to re-coil during the stringing process, making handling easier.

Dynamic resilience of a stringbed will determine how well it can deform (absorb energy), return upon ball impact and provide the greatest energy return. The more dynamically resilient the string (or string plane), the greater the deformation and therefore the greater the energy return. Over a period of time and play, string tends to lose the ability to conform to its original shape, gradually imparting a different feel to the racquet and ultimately playing "dead."

Tensile strength is the force required to break the string during a straight pull. Generally, strings with higher tensile strength will have a higher breaking point. One of the biggest challenges for a racquet technician is dealing with string wear and string breakage. Chronic string breakers have increased in numbers since the advent of wide body racquets. Wide body racquets tend to be stiffer than standard width frames. As a result when balls hit the strings very close to the frame, they can cause shearing or overload breakage. Although this type of string breakage near the frame can also be caused by worn or cracked grommets. Open string patterns also allow more string movement and cause frictional notching — the main reason for string breakage among tennis players who hit with spin.

Keep this information in mind when recommending a racquet for excessive top-spinners. While they'll love the extra bite on the ball that an open pattern allows, they'll blame you for breaking strings every week! There are a few ways to cure the chronic string breaker blues. First, a thicker version of their favorite string (if available) will offer similar playing characteristics but with slightly less feel. String savers are another way of reducing the "sawing" action of the mains against the crosses and can be used with their string of choice. Next, try using durability oriented synthetic strings. Finally, various hybrids (two different types or gauges of string in the same racquet) can be used to extend string life while still keeping costs reasonable. Probably the most effective hybrid available for reducing frictional notching combines Kevlar mains with nylon crosses. Be prepared to lower tension about 10% on these strings, though, to reduce the stiff, harsh feel of Kevlar which has about 3% elongation at 60 pounds.

Some players may ask you to tell them how much longer their strings will last with Kevlar. Keeping accurate records is a great way to address this situation. However, simply inspecting the strings for notching and a "wear pattern" may provide you with the knowledge you need to approximate whether the strings will last through the next match or the next month.

With the advent of wide body racquets, a new phenomenon has developed, shock breakage or shearing of string near the frame. As frame cross-sections (beam height) increased, so did frame stiffness, requiring the strings to accept more load during ball impact. Consequently, racquetball, squash and tennis players are sometimes paying the price of off-center hits by having to restring. Using a thicker gauge or a multifilament string can help. (Keep in mind that increasing string thickness by one gauge can add 5-10 grams to overall racquet weight. A typical coil of 16 gauge nylon string weighs 15-20 grams.) If a customer is chronically breaking strings in the upper hoop near the frame, be sure to check the grommets for telltale wear or cracks. However, if the grommet barrels and bumper are in good condition, you might want to tube the center 6-8 mains at the head and/or consider a different string for your customer.

Frame Technology

(MRT applicants only)

A variety of methods are used to manipulate stiffness, weight and balance. Pre-wide-body frames relied solely on material placement in determining the stiffness of a frame. Some frames were stiffer in the shoulders, some stiffer at the tip as a result of placing higher modulus graphite or boron in these areas. Today, manufacturers enjoy the added variable of adjusting beam height or cross-section to make a frame stiffer or more flexible. Materials aside, increasing the cross section of a frame during production is the most effective way to increase stiffness. Increasing stiffness will increase frame shock and frame vibration. Frame shock is the force felt at the moment of impact. Frame vibration is the lasting movement or noise after the ball has left the strings. The most effective way to reduce shock is to add weight to a frame.

Weight and balance have moved to the forefront in frame design as manufacturers seek ways to improve maneuverability. Wilson's Hammer Technology (for tennis and racquetball) popularized lightweight, head-heavy frames. Most conventionally weighted tennis frames feature added weight at the butt end, ranging from 1-3 ounces. This helps counter the predominance of weight in the hoop area resulting in a head-light balance. Conversely, most lightweight, head-heavy frames remove weight from the butt end to reduce overall weight, while retaining a similar swing weight of a conventionally weighted and balanced frame. To increase a racquet's torsional stability (resistance to twisting), a manufacturer or a technician can increase grip size, add weight to 3 and 9 o'clock positions, make the hitting surface of the racquet head wider, or apply a high-friction grip.

Today's longer racquets can offer players a variety of benefits, including more reach, more power, more spin and reduced torque. Each additional inch increases power by 10%, all other things being equal. Longer racquets also generate more racquet head velocity, thus creating the potential for more spin. A racquet that is one inch longer can increase a player's court coverage by about 5%, while a two-inch longer racquet can increase court coverage by about 13%. Contrary to intuition, longer racquets can actually reduce the amount of torque, or twisting, experienced by off-center hits.

Not all players will benefit from longer racquets, so extensive play testing is recommended. Be sure each player who play tests a long racquet uses it in a match situation, hitting a variety of different shots.

Back to Basics

Seven Factors that Determine Stringbed Stiffness

When you talk tension with customers, you're actually talking stringbed stiffness. But tension is just one piece of the puzzle that determines how a stringbed feels to a player. A player normally feels one of three distinct stringbed sensations: loose (springy or lively); tight (hard, jarring, stiff); or dead (elongated, mushy, or 'bagged out'). Seven separate factors cumulatively determine overall stringbed stiffness and therefore the player's perception of power, feel, and control.

Head Size/String Length

While most stringers are aware that head size variations affect stringbed stiffness, most players aren't as savvy. If a customer changes from a midsize to an oversize frame and asks for the same tension, how should you respond? Most manufacturers do take head size differences into account when determining tension ranges. String length is a major factor. Longer strings must be strung at a higher tension to achieve the same stringbed stiffness as with shorter strings. According to Dr. Howard Brody, to change from one frame size to another (while retaining similar playing characteristics from the strings), the tension-divided-by-string-length ratio must be similar. (Sixty pounds of pull [machine] tension on an oversize frame's main string will produce a lower actual tension than the same 60 pound pull tension on a midsize frame's main string.) So when that customer who's just changed from a midsize to oversize frame says, "String it at 60 pounds, like before," you can explain why he might want to increase tension by a few pounds. Why then are shorter cross strings looser than longer main strings? Other factors come into play here, mainly the friction of the crosses being pulled through the mains. It's not uncommon for a racquet to have main strings with 55 pounds of tension and crosses with 40 pounds. Matching main and cross string tensions would require increasing tension on the crosses to the point of deforming and probably damaging the frame. Also, the resulting stringbed stiffness would certainly be too high for most players. So, when that same customer shows up with a Stringmeter demanding to know why the crosses are so much looser than the mains, you can confidently explain why.

Pattern Density and Staggered Strings

Many frame makers have been redesigning string patterns on new racquets to meet specific objectives. Some increase string density in wide bodies to help maximize string life. Many also assert that a denser string pattern increases control for certain types of players. Or designers may increase string spacing to offer players more spin potential. Generally speaking, a more open string pattern yields lower stringbed stiffness than a dense pattern. Whether either one provides more control depends on style of play (for tennis players). Spin players may claim increased control on an open pattern because the strings can embed deeper into the ball, whereas a flat hitter finds more control with a dense pattern due to the increased stringbed stiffness. Players using open string patterns should be prepared to restring more often though. The increased string movement can cause notching and premature breakage. Denser patterns have become more popular in wide bodies to help increase string durability. In badminton, dense patterns allow stringing at very low tensions, while maintaining a reasonable stringbed stiffness. When stringing badminton frames, it's best to use the smaller badminton clamps to accommodate these denser patterns and not damage the string.

A few racquet manufacturers (Dunlop, Gamma, Prince) have introduced models that feature splayed, or staggered string patterns. Offered under a variety of names, each of these string systems is slightly different from the next, but all are similar in concept. Each string enters the frame on a different level, or plane, than the previous string. Due to the increased angle of each string entering the stringbed, string vibration is reduced. Also, overall stringbed stiffness is increased when tensioned the same as a conventional string pattern. Consequently, recommended tensions for staggered string racquets are typically lower compared to conventionally strung racquets. Another effect of these string systems is that cross strings alternate between "easy" and "hard" weaves that result in decreased tension on every other cross string. When stringing staggered string racquets, it's important to lock in the top (1X) cross with a "hard" weave. Otherwise, the outer mains and crosses will be floating, causing excessive vibration and not achieving their desired effect.

String Gauge

This factor causes more confusion than any other. If you string two identical racquets with different gauge (but otherwise identical) strings and perform the palm test with the strung racquets; the thinner gauge will have a higher harmonic pitch or "ping." Most people would logically assume the thinner string is tighter. Even though we found little difference when measured statically (i.e., RA Test), the racquet with thinner gauge may feel less stiff in play, due to the greater elasticity of the thinner string. Dr. Brody reports that, generally, a 17 gauge string will be about twice as elastic (100%) as a 15 gauge string, all other factors being equal. This increased elasticity results in lower dynamic stiffness (meaning the strings will feel more elastic) during ball contact. A player changing to a thicker string (for greater durability, for example) may complain that the "ping" isn't the same as with his thinner gauge string. However, increasing tension to reproduce that harmonic pitch would probably result in a stringbed stiffness too hard for his liking. So string for feel, not for the "ping."

Below are the Tennis Industry Association's gauge standardization specifications.

U.S. INTERNATIONAL DIAMETER (mm)
13 12 1.65-1.80
14 11 1.50-1.65
15 9.5 1.41-1.49
15L 9 1.33-1.41
16 8.5 1.26-1.34
16L 8 1.22-1.30
17 7.5 1.16-1.24
18 7 1.06-1.16
19 4 .90-1.06
20 3.5 .80-.90
21 3 .70-.80
22 2.5 .60-.70

String Type

Stringbed stiffness differences between nylon and aramid fiber (Kevlar®, Technora®) strings are well known. Aramid is stiff. To compensate for the lesser elongation of aramid, most companies recommend decreasing overall tension settings by 10%. This may concern players trying a aramid hybrid for the first time, but assure them the reduction is necessary to maintain the most acceptable playing similarities. Less significant variations may also be noticed with Zyex® blends and various nylon string constructions (i.e., coreless microfilaments, center-cored multifilaments, and outer-wraps variations).

Machine or Pull Tension

This one's pretty obvious; your machine's tension setting can have the greatest overall influence on stringbed stiffness. When you tell your customer 60 pounds, make sure your machine is giving you 60 pounds. Our rule of thumb: recalibrate every 20 to 25 string jobs, when making large tension adjustments, or whenever you move your machine.

Stringing Machine Type

Expect a stringbed stiffness difference between racquets strung on spring tension and continuous tension machines. Continuous pull machines, whether drop-weight or electronic (Babolat, Prince, Alpha, Gamma, etc.), will normally produce a firmer stringbed than will identically calibrated spring tension machines. A continuous tension machine (as the name implies) maintains a constant tension on a string to compensate for elongation and clamping, which generally results in a 10% firmer stringbed.

Stringer Technique

Finally, all stringers have different techniques. Tensioning string from varying distances, double pulling and pre-stretching all contribute to affect overall stringbed stiffness. Such varying techniques may be one explanation for small deviations in stringbed stiffness that occur even between two different stringers working in the same shop on the same machine. For example, we recorded single pulling and double pulling techniques (on a 1.25 mm nylon), using a spring tension machine — with varying results.

Conclusion

Our test results indicate that pull tension, head size, and string density have the greatest impact on overall stringbed stiffness. String gauge apparently makes the least difference in static testing, though most good players can feel the difference during play. What we refer to as "tension" is really the complex result of the seven interacting factors discussed here. Changes in any of these variables may affect the feel of a racquet and the way it plays. By knowing these factors and how they can affect stringbed stiffness, you can bring out the best in any frame and be a more knowledgeable advisor to all of your clients.

Rules of Tennis

Official Code of International Tennis Federations (ITF)

Rule 4 (excerpt): The Racket

Rackets failing to comply with the following specifications are not approved for play under the Rules of Tennis:

(a) The hitting surface of the racket shall be flat and consist of a pattern of crossed strings connected to a frame and alternately interlaced or bonded where they cross; and the stringing pattern shall be generally uniform, and in particular not less dense in the centre than in any other area. The strings shall be free of attached objects and protrusions other than those utilized solely and specifically to limit or prevent wear and tear or vibration and which are reasonable in size and placement for such purposes.

(b) The frame of the racket shall not exceed 29 inches (73.66 cm) in overall length, including the handle and 12½ inches (31.75 cm) in overall width. The strung surface shall not exceed 15½ inches (39.37 cm) in overall length, and 11½ inches (29.21 cm) in overall width.

(c) The frame, including the handle, shall be free of attached objects and devices other than those utilized solely and specifically to limit or prevent wear and tear or vibration, or to distribute weight. Any objects and devices must be reasonable in size and placement for such purposes.

(d) The frame, including the handle and the strings, shall be free of any device which makes it possible to change materially the shape of the racket, or to change the weight distribution, during the playing of a point.

Manufacturer Technologies

(MRT applicants only)

The following is a compilation of information taken directly from industry product catalogues and technical manuals. No USRSA endorsement of any product or claim is intended.

Babolat Technologies

Aero Modular Technology — New frame concept with high modulus graphite, varying beam profiles at 3 strategic locations offering power and control, while increasing head speed. Thinner cross-section at tip to increase power. Standard cross-section at side of head to improve stability. Wide cross-section at throat to increase control and allow a faster swing.

Carbon Xtrem — Layers of carbon braided on 3 different angles are placed on the head of the racquet for optimized hitting performance.

Cortex System — throat system designed to filter out vibrations which interfere with feel, in order to enhance the feel of the ball.

Elliptic Geometry — optimal cross-section shape designed to offer best resistance to torsion. Makes frame 20% stiffer for more power.

GT (Graphite Tungsten) — Improves racquet performance, based on the concentration of Tungsten fibers at various strategic parts of the frame. A greater concentration of Tungsten in the head of the racquet strengthens the frame to reduce torque for greater precision (26% more precision compared to the previous Pure Drive).

Smart Grip — first ever, truly ergonomic racquet handle perfectly shaped for your hand. The entire palm of the hand is in contact with the grip. As of 2009, Smart Grips are adjustable and removable.

Woofer — Grommet system that permits all the strings to work together to their full potential when strings contact the ball thanks to piston and pulley functions. It is designed to deliver 10% more power, enlarge the sweetspot, enable 25% more contact between the ball and the strings, and absorb the shock and vibration from ball impact.

Zylon Matrix — a material with incomparable stiffness (50% stiffer than standard carbon) is placed in key areas of the racquet. Used in head of frame to reinforce torsion making the frame more stable and more comfortable. Used in the throat to increase stiffness for more power.

Dunlop Technologies

4D (4D Braiding) — Braiding four differently angled layers of graphite into a single layer, achieves the strength and stability of a traditional 4-layer construction (producing 33% more control) while still retaining the softness of a one-layer construction (generating 33% more feel).

Aerogel — The world’s lightest solid has a strength up to 4,000 times its own weight. Delivers an unmatched strength-to-weight ratio for enhanced stiffness and increased power.

ISIS (Impact Shock Isolation System) — Dampens frame shock and vibration through a decoupling handle.

Vibrocore — Made up of a thermal-plastic resin with a silicon core inserted into the throat of the racquet. The racquet is actually cut in half and re-constructed with the Vibrocore System dramatically reducing shock at ball impact.

Fischer Technologies

AirCarbon — a material developed for the aircraft industry. It has 50% higher strength properties than conventional fibers and results in a racquet design with maximum resistance to twisting with minimum weight.

Cap Grip — uses thermoplastic materials to absorb vibrations.

Direct Energy System (DES) — dual tube construction in the shaft enables maximum torsional stiffness and revolutionary weight distribution.

Fischer Stability System — utilizes metal platelets at 3 and 9 o’clock that give the frames increased weight, and stability on both sides of the head. It is designed to improve control of ball direction on off-center hits.

Frequency Tuning (FT) — racquets feature a Precious Metal Matrix that is applied to the entire surface of the racquet in precise amounts and locations to optimize the weight distribution of the frame. This optimization is designed to make the various vibration frequencies of the racquet “tune” with one another. Frequency Tuning (FT) racquets provide greater power with less shock as well as greater feel and more control.

FTi — Frequency Tuning frames that also utilize titanium.

Grip Dual System (GDS) — As the name would imply, the grip is made of two parts. GDS is designed to reduce impact shock and eliminate torsional vibration from off-center hits.

Magnetic Speed — Technology utilizing magnets at 3 & 9 o’clock. The magnets are equally polarized so that as the sides of the frame move toward each other during impact with the ball, the magnets repel each other causing the frame to return to original shape more quickly. This quick return to original shape causes the ball to be returned with greater power.

Trapezoidal Profile — a special box-shaped racquet profile designed to reduce arm strain.

Twin Tec — twin tube construction in the shaft prevents vibrations reaching the grip area and offers maximum arm protection.

Vacuum Technic — a manufacturing technique designed to remove any air pockets from the layers of graphite. This results in a frame that is homogeneous and stress free.

Vibra Stop — The Vibra Stop’s design allows it to dampen vibrations, give players an excellent grip, and it’s even washable.

Gamma Technologies

Aero Beam — Aerodynamic frame shape reduces air resistance and allows easier maneuverability. Also gives the perfect amount of flex in the head to store power for maximum ball speed.

Integrated Stability System (ISS) — incorporates extra weight positioned at 3 and 9 o’clock to reduce torque for maximum stability, energy transfer and control.

Power Step — Larger rectangular cross section for greater power and torsional stiffness that steps down an aerodynamic cross section to reduce aerodynamic drag.

HEAD Technologies

Airflow — combination of three important features that are essential for a woman’s racquet; Lightweight, Perfectly Balanced and an Ergonomic Grip.

AnTi.Torsion — utilizes a crossbar in the throat to improve torsional stability on off-center hits.

CrossBow — The world’s first dynamic bridge racquet construction. The bridge is suspended from the frame and moves independently, which allows the racquet to store energy in both the stringbed and the bridge. The CrossBow acts like a spring or bow that is loaded during ball impact. This new-found energy is unleashed providing incredible power. CrossBow also enlarges the sweetspot because it has 10 main string going through the dynamic bridge.

d3o — a member of the smart materials category, can change its behavior during impact. Integrated in the lay-up and positioned in the shaft area of HEAD’s Youtek tour racquets, d3o is able to sense the needs of the player during different strokes. On high-speed impacts (aggressive shots), the smart molecules lock together within nanoseconds and dramatically increase the stiffness of the racquet to provide maximum power. On low-speed impacts (slices or drop shots), the material stays in its relaxed state absorbing the impact to provide a softer touch for better feel and control.

EDS (Electronic Dampening System) — active and electronically controlled system, consisting of piezoelectric fibers, a flex circuit and a microchip. These substantially reduce initial shock impact (by 50%) and vibrations twice as fast as a conventional racquet resulting in significantly reduced stress on the arm.

Ergonomic Grip System — new grip shape on AirFlow racquets that is tapered thicker at the bottom and thinner at the top. This is much easier to hold for a woman’s hand and provides less arm fatigue and better control.

Extreme — increased head width, which can allow the ball to slide further across the stringbed for unmatched spin generation for players with a modern playing style.

FlexPoint — features two precisely-engineered control holes in the racquet’s head. This creates a new point of flex, which cups the ball and improves control without losing power.

HEAD Grommets with Teflon — friction reducing polymer creates a self-lubricating effect in the base material allowing the string to slide though the grommets wit nearl no friction for much less engery loss and providing much more power.

Head Stabilizer — located in the shaft of the racquet — HEAD uses a metal mass between a rubber elastomer to counteract the frame’s oscillation on impact and eliminate racquet vibration and ensure the ultimate in comfort on every shot.

Intelligence —Special Intellifibers at 4 & 8 o’clock take the mechanical energy created by contact and convert it into electrical energy, which is used to stiffen the frame providing power, comfort and dampening.

IntelligenceX — an evolved version of Intelligence. Intelligence X adds Intellifibers to the racquet head (not just the shaft) to increase the torsional stability up to 42% for extra precision and accuracy. These added Intellifibers are placed at 2 and 10 o’clock.

ISD (Integrated String Dampener) — an integrated string dampener fixed onto the grommets at the throat to reduce string vibration.

Liquidmetal — this material has a unique liquid atomic structure that does not deform on impact. Results in little to no energy loss giving ultimate energy return, which translates into pure energy and perfect power (29% more power).

LMS (Longer Main String) — by lowering the bridge section in a new throat design, creates a larger hitting surface without making the racquet any bigger.

Metallix — made of a specially designed matrix of carbon fibers and a new crystalline metal alloy. This alloy’s grain-size is 1000 times smaller than that of a typical metal. The decreased grain size results in a lighter, stronger, and more powerful racquet.

MicroGel — a new silicone-based material with the lowest density of any material. Combined with stiff and strong composite fibers to create a racquet with incredible responsive qualities. On ball impact, MicroGel uniformly distributes the impact load around the frame to provide the most rock-solid feel and superior touch.

NoShox — a newly-developed memory foam integrated into the racquet handle that reduces racquet vibrations by more than 27%.

PowerFrame — features an innovative cross-section design with dual rounded bubbles in the throat and shaft area of the racquet, reducing weight and increasing torsional rigidity.

Protect System — tennis elbow protection technology integrating the racquet, grip, and string.

Total Sweetspot Construction (TSC) — utilizes corrugated construction to increase torsional stability in the racquet head. This extends the sweetspot throughout the entire racquet head providing excellent control.

Youtek — incorporates different technologies to give you the individual benefits you need to match your playing style. In HEAD’s tour racquets, YOUTEK includes d3o, HEAD Grommets with Teflon, and Aramid bumpers.

Prince Technologies

AirBridge — Provides for greater support and stability in the yoke area of the frame.

Carbon Wave Matrix — Aligns the graphite fibers in a wave pattern to complement the angular orientation of the other layers.

Cross-Bar Stabilizer — Located in the mid-shaft area of the racquet, increases the stability of the frame.

Cushion Grip System — This 3D molded Thermoplastic Rubber handle absorbs 56% of the shock of ball impact allowing for maximum handle comfort.

Double Bridge — Thermoplastic rubber elastomer located at the top of the throat and in direct contact with frame and string. Reduces frame shock and string vibration.

Dynamic Braid — Carbon fibers are braided in the shaft area to provide a slightly stiffer feel at the zone where the braid is incorporated.

EXO3 — Utilizing Prince’s patented Energy Bridge and Energy Channel technologies, EXO3 captures up to 26% of the wasted energy at impact and re-directs it back into the ball for 25% more spin, 26% more control, 50% less frame vibration and an 83% larger sweet spot.

EXO3 Energy Bridge — Patented 100% solid carbon fiber bridge, designed to suspend the stringbed from the racquet providing superior comfort with feel and a supersized sweetspot.

EXO3 Energy Channel — Radical new frame design that redistributes mass to the outer most edges of the frame providing the ultimate in racquet stability.

O3 — Giant O Ports replace traditional size string holes. O Ports are designed to significantly increase the sweetspot and improve racquet head speed.

O3 Speedport — wind tunnel testing proves O3 Speedport racquets move through the air up to 24% faster than traditional racquets. Speedports also strengthen and stabilize the frame for up to a 59% bigger sweetspot.

PowerLine — A reinforced beam with grooves on the inside surface of the frame increases frame strength while providing more power in a lighter racquet.

Speedport Tuning System — Patented system allowing players to customize their O3 Speedport Black or O3 Speedport Tour frame with either Port inserts or Hole inserts. The Port option offers a softer hitting feel, string damping and a larger sweetspot. The Hole option offers a firmer hitting feel, more string feedback and a traditional sweetspot.

Strung Thru Stringing System — Featured in the O3 Speedport Platinum and Gold frames, it provides the option of stringing through the throat of the racquet. The Strung Thru option provides up to a 70% larger sweetspot.

Sweet Spot Expansion — Slotted grommets allow maximum freedom of movement for strings resulting in a larger sweetspot.

Triple Threat — a unique balanced weighting system utilizing increased weight in 3 loactions; 10 o’clock, 2 o’clock, and the handle. This creates a larger sweet spot in every direction, ultimate stability for increased power and control, and reduced arm shock.

Tungsten — added to Triple Threat technology in some frames to further improve stability.

Variable Damping System — The dampener in the O3 Speedport Silver, Blue and Red frames can be positioned on the strings for maximum dampening or positioned in the throat of the racquet for medium dampening.

Prince gives each of its racquets power level ratings (determined by a formula incorporating headsize, stiffness and length), which increase as the power level of the frame increases.

Wilson Technologies

Double hole — Bigger holes on the entire racquet resulting in a smoother feel, softer string bed and a little extra power.

FX — the next generation of Wilson [K] Factor tennis racquets. An innovative Quad Shaft frame geometry developed to provide greater stability, distributing weight to 4 pillars instead of 2.

Hammer — weight is taken out of the handle of the racquet and maintained in the head of the frame. The result is increased power and stability for lighter weight racquets, as well as a higher and larger sweet spot.

Iso-Zorb Grommets — grommets made out of softer shock absorbing material (generally placed at 6 o’clock) provide a more comfortable and cleaner playing racquet.

[K] Factor — combines the next generation in nanotechnology and unique frame engineering innovations, that result in the ultimate line of [K]ontrol racquets for all player types. Made up of 4 key technologies: [K]arophite Black, [K]onnector, [K]ontour Yoke, and [K]ompact Center. Not all frames utilize all 4 technologies.

[K]arophite Black — a next generation structure created through a unique process at the nanoscopic level resulting in more feel and a stronger and more stable racquet.

[K]ompact Center — new industrial design innovation that improves handling, maneuverability and provides additional feel.

[K]onnector — 2 external wings molded into each side of the hoop to increase dwell time. This provides greater control and comfort with a larger sweetspot.

[K]ontour Yoke — new frame engineering technology that enhances stiffness at key stress points on the racquet for improved torsional stability.

Nanofoam — a new exclusive foam material used to fill the frame at specific points for a quieter and better feeling frame.

nCode — Nano-sized silicon dioxide crystals are used to permeate the voids between carbon fibers. The end result is a racquet that is 2x stronger, 2x more stable and up to 22% more powerful.

nZone — Building off of the heritage of Wilson’s PowerHole patented technology, nZone are keyhole shaped holes strategically placed (usually at 3 and 9 o’clock) for increased sweet spot, more forgiveness and power.

Perimeter Weighting System (PWS) — extra weight is placed at 3 and 9 o’clock for increased torsional stability.

Triad — Frames are made up of 3 separate pieces. The hoop and the handle are separated by a shock absorbing material called Iso-Zorb. The technology is designed to stop the shock of impact from reaching the handle.

Volcanic Cross Section — frame geometry with large flat surfaces. It provides more stability in light-weight frames while maintaining maneuverability and power. Especially designed for nCode racquets.

X-Loop Geometry — unique flat and rounded frame geometry, which is inverted at the hoop and yoke transition. Results in increased stability.

Wilson labels most of its racquets with a swing index (S.I.) rating, which is generally higher on softer frames.

Yonex Technologies

3D Carbon Sheet — by weaving carbon fibers in 3 directions, the pulling strength is equalized in 3 directions meaning the shaft has greater resistance to twisting forces.

3D Shaft — the shaft is sculpted into a surf board like shape to provide advanced face stability.

4XP Isometric — developed for a wider sweet spot. By indenting the 4 corners of the frame, a greater number of main and cross strings are equalized to enlarge the sweet spot by 13%.

Aero-Box Vari-Frame — combines the aerodynamic profile of a frame head that is pared on the sides with a squared upper and lower frame section and additional Tungsten IPS weighting. Reduces wind drag by 10%.

Aero Shape — Creates more frame thickness for higher repulsion.

Cup-Stack Carbon Nanotube — applied in the racquet frame, which enables the frame to give players the right amount of flex to stay with the ball, and quick repulsion to make the full energy available for power return.

Dual 3D Stabilizer — integrates 3D Carbon Sheet into the shaft to provide more face stability and more racquet maneuverability.

Dual Power Structure — utilizes different frame cross sections in the frame (Power Frame) and shaft (Power Shaft) of a racquet.

Elastic Ti — nanoscale alloy that combines extremely low elasticity and high strength. It has 44% lower elasticity and 8% higher strength compared to previous best titanium alloy.

F2Filter Grommet — by combining a metallic powder with the grommet, the unnecessary vibration and sound at impact will be reduced.

Feel Control Grommet System — has an 18% deeper channel at the top and side of the frame…thicker grommet that adds a cushioned feel with crisp response.

Flex/Torsion Control Shaft — widened front width of the shaft by 14% compared with an ordinary racquet. This width advantage increases the racquet’s ability to provide high repulsion power and maneuverability.

Hexagon Cross Section — by uniting box and triangular shape sections, a solid feeling at impact has been realized by providing better head speed and maneuverability.

Integrated Power Weight System (IPS) — places weight strategically at 3 and 9 o’clock to help reduce torque and compensate for off-center hits.

Isometric Head Shape — allows for more strings of equal length, creating a larger sweetspot.

Metal Hybrid IPS — utilizes a metal hybrid 10 times heavier than high modulus graphite.

Nano Silver Grip — utilizes a nano-scale silver compound in the grip itself that provides a combination of comfort and anti-bacterial elements.

Nano Technology Matrix C60 — Utilizing nano-technology, resin is compounded with fullerene to create “Matrix C60.” This is used to bind individual carbon fiber filaments and increase the mutual attraction power of resin and carbon fibers.

Oval Pressed Shaft (OPS) — gives a racquet more spin, control, and feel for the ball by flexing on impact and increasing the time the ball is on the strings.

Power Frame — the new aerodynamically-contoured upper section of the racquet head reduces air resistance and allows a crisp follow through. It also gives the ideal amount of head flex to store the power and hit the ball with maximum speed.

Power Isometric — a wider Isometric area that increases the already large Yonex Square Head sweetspot by 20% compared with a conventional round head racquet. The construction yields more power and more repulsion.

Power Shaft — the nano-science process concentrates more fibers in the lower third of the head and throat to provide the ideal stiffness for high stability, high repulsion, and maximum return of energy to the ball. The channel at the side of the shaft is a new structure to prevent torque at impact. This helps to make a thinner, but stiffer frame, so full power is transferred directly to the ball.

Soft Grommet — there are soft grommets located at the four corners of the frame. These grommets are designed to reduce the shock from off-center hits, widening the sweet spot still further.

Soft Grommet II — construction featuring Soft Grommets plus an additional high-strength plate for greater durability and protection against damage when the frame strikes the ground.

Shockless grommets — soft grommets placed in the throat and the 3 & 9 o’clock positions to absorb vibration, reduce shock, and optimize feel.

Super Cushion Grip — the cushioned underside layer of this grip reduces vibration, further enhancing the soft feel at impact provided by Shockless Grommets.

Titanium Mesh — used to increase power and maneuverability without increasing the weight of a racquet and ensure a racquet frame resists twisting.

Ultimum Ti — a racquet material that delivers twice as much responsive energy as carbon fibers and is three times stronger than Titanium.

Yonex also recommends that racquet technicians string its racquets at different tensions for different grip sizes. The recommended tension range for a racquet will be found in the throat of the racquet because even with the same model, a 4½" grip will have a higher recommended tension range than a 4¼" grip.

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