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Playtest: Wilson (K) Gut Pro 16

By Greg Raven

Wilson (K) Gut Pro is a premium multifilament made of high crystallinity xycro microfibers bonded together with polyurethane. Fluorocarbon (polytetrafluoroethylene) microfibers are interspersed among the xycro microfibers for enhanced performance. According to Wilson, (K) Gut Pro is engineered for maximum control, and is more durable that (K) Gut. (See our playtest report of (K) Gut on-line at tennisindustrymag.com.) (K) Gut Pro is also pre-stretched for a crisp feel and minimum tension loss. Wilson recommends (K) Gut Pro to any player who wants a string with excellent control, gut-like comfort and feel, and enhanced durability.

(K) Gut Pro is available in 16 (1.33 mm) and 17 (1.28 mm) in gray only. It is priced from $20 for sets of 40 feet. For more information or to order, contact Wilson at 773-714-6400, or visit wilsontennis.com.

In the lab

We tested the 16-gauge (K) Gut Pro. The coil measured 40’. The diameter measured 1.32-1.35 mm prior to stringing, and 1.27-1.29 mm after stringing. We recorded a stringbed stiffness of 74 RDC units immediately after stringing at 60 pounds in a Wilson Pro Staff 6.1 95 (16 × 18 pattern) on a constant-pull machine.

After 24 hours (no playing), stringbed stiffness measured 65 RDC units, representing a 12 percent tension loss. Our control string, Prince Synthetic Gut Original Gold 16, measured 78 RDC units immediately after stringing and 71 RDC units after 24 hours, representing a 9 percent tension loss. (K) Gut Pro added 16 grams to the weight of our unstrung frame.

In our lab testing of 688 strings, we found that (K) Gut Pro 16 has a stiffness of 182 lbs/in. and a tension loss of 10.62 lbs., putting it in the top 20 percent of strings in terms of softness, and the top 20 percent in terms of tension maintenance. Comparing it only to other synthetic strings, (K) Gut Pro 16 is in the top 15 percent in each of these categories. You can read about our lab test procedure here.

The string was playtested for five weeks by 35 USRSA playtesters, with NTRP ratings from 3.5 to 6.0. These are blind tests, with playtesters receiving unmarked strings in unmarked packages. Average number of hours playtested was 26.9.

There are no special stringing instructions for (K) Gut Pro. We found that (K) Gut Pro is easy to handle during stringing, although we did have some problems with blocked holes due to its softness.

No playtester broke his sample during stringing, one reported problems with coil memory, none reported problems tying knots, and two reported friction burn.

On the court

In our playtest team’s judgment, (K) Gut Pro 16 is above average across the board, and well above average in Touch/Feel and in Resistance to Movement, out of the 127 strings we’ve playtested to date for publication. It would normally be anomalous to have a polyurethane-impregnated string score highly in Resistance to Movement, but in this case (K) Gut Pro follows in the footsteps of (K) Gut, which scored well above average in this category.

Four players broke the string during the playtest period, one each at 6, 15, 21, and 27 hours.

Two playtesters broke the sample during testing, one at three hours and one at 14 hours.

Conclusion

As we predicted in our playtest report of (K) Gut, Wilson is refining its use of fluorofibers in tennis string. By reducing the power and improving the durability of (K) Gut, while maintaining its benefits, Wilson’s (K) Gut Pro should appeal to heavier hitters who are looking for a premium nylon string to augment their game. One of the truly amazing things about (K) Gut Pro is how “balanced” its scores are from category to category. In fact, (K) Gut Pro has the best across-the-board balance of any string we’ve ever playtested. Based on this metric, we’d have to say that no matter what you want from your string, (K) Gut Pro is likely to deliver, and you won’t have to sacrifice anything else to get it.

Playtester comments

“Incredible spin from the back court, and good pop on volleys.” 5.5 male serve-and-volleyer using Wilson nBlade strung at 60 pounds LO (Wilson NXT 16)

“This is a very arm friendly string with excellent spin and control.” 5.0 male all-court player using Babolat Aeropro Drive strung at 58 pounds CP (Kirschbaum Competition 16L)

“This string absorbs shock very effectively. Excellent comfort and control.” 4.0 male baseliner with heavy spin using Vîlkl DNX 8 strung at 57 pounds LO (Luxilon Timo 122 17)

“Caution must be exercised during installation to avoid friction burn. This string has outstanding comfort and spin. The bite is very pronounced. Slice shots are piercing and heavy. This is an exceptional string.” 4.0 male baseliner with heavy spin using Dunlop 200G strung at 58 pounds CP (Prince Synthetic Gut Original 17)

“Excellent comfort and playability. The string bed has a great feel with a wonderfully crisp response.” 3.5 male all-court player using Dunlop M Fil 300 strung at 64 pounds LO (Prince Synthetic Gut w/Duraflex 16)

“This is a very arm friendly string. Great feel and touch. Placement is easy. Big swings can be executed with great confidence.” 5.0 male all-court player using Wilson Pro Staff Trance MP strung at 62 pounds LO (Wilson Sensation 16)

“This string has plenty of spin, power, and touch. The comfort is excellent.” 4.0 male all-court player using Pro Kennex Core 1 No. 10 strung at 65 pounds LO (Pacific X Force 17)

“High marks across the board. Great power, control, and touch. Comfortable, but not mushy.” 4.5 male all-court player using Pro Kennex Kinetic Pro 7g strung at 67 pounds CP (Babolat Pro Hurricane 16)

“This string has more control than any multifilament I’ve tried.” 3.5 male all-court player using Vîlkl Tour 10 MP strung at 53 pounds LO (Wilson NXT 17)

“This is a good all-around string which should appeal to a wide audience. It compares favorably with the best multifilaments on the market. The comfort and control are exceptional.” 5.0 male serve-and-volleyer using Wilson nTour strung at 59 pounds CP (Natural Gut 16/17)

“Stringing is quick and easy. This is a comfortable, all-court control string. It has a nice crisp pop on volleys and a solid feel on ground strokes. It does not lose playability over time.” 4.0 male all-court player using Prince O3 Red MP strung at 54 pounds CP (Gamma TNT2 Pro Plus 17L)

“This string has a comfortable feel. It is also quite durable, making it a good option for string breakers who want to try something besides polyester.” 4.5 male all-court player using Prince O3 Hybrid Tour (16x18) strung at 62 pounds LO (Prince Premier w/Softflex 16)

“String installation is very easy. There is some minor clouding and the coating is a tad sticky, but the crosses weave quickly. Phenomenal control, comfort, and power. There is some extra pop on serves and volleys. The strings tend to move a lot. Because tension maintenance is above average, playability lasts for a long time.” 3.5 male serve-and-volleyer using Wilson KPro Open strung at 56 pounds LO (Gamma TNT Fat Core 17)

“For a nylon multifilament, the control, durability, and tension maintenance are very good.” 5.0 male all-court player using Prince O3 White MP strung at 60 pounds LO (Wilson Sensation 16)

“Great playability and durability. String breakers looking for a more comfortable option should give this a try.” 5.0 male all-court player using Head MicroGEL Radical MP strung at 63 pounds LO (Tecnifibre Promix 17)

“This is a good all-around string, but it lacks the “wow” factor. It has good tension maintenance and very little string movement.” 4.5 female all-court player using Prince O3 Tour MP strung at 56 pounds CP (Tecnifibre Synthetic Gut 15L)

“This is a very comfortable string with surprising durability and control. It will appeal to a wide range of players.” 6.0 male all-court player using Wilson nTour strung at 55 pounds LO (Wilson NXT 16)

“Great control and tension maintenance. The playability and feel are slightly lacking.” 4.0 male all-court player using Wilson nTour Two strung at 55 pounds LO (Wilson Reaction 16)

“This string feels solid and comfortable at impact. It does not seem to have high elasticity, so the energy return is low. Given the low trampoline factor, big swings are very easy to control. Power baseliners looking for more comfort will love this string.” 3.5 male all-court player using Wilson KSting strung at 64 pounds CP (Wilson Sensation 17)

“This is a high playability multifilament. Power is on the low side. It holds tension remarkably well.” 5.0 male all-court player using Vîlkl DNX 9 strung at 52 pounds CP (Gamma Live Wire XP 17)

“This string feels solid at impact. It has great feel and touch. The control suffers slightly after the initial tension loss, but nothing out of the ordinary.” 5.5 male all-court player using Fischer M Tour (SL) strung at 59 pounds CP (Vîlkl Power Fiber II 16)

“This string performs beautifully in a tournament setting, where confidence is necessary. Given its superior control, it handles low tension remarkably well. I never get the feeling that the ball is going to spray.” 5.0 male serve-and-volleyer using Vîlkl Tour 10 V Engine MP strung at 40 pounds LO (Polyester 16)

“Installation is very easy. Though soft, this string pulls quick and does not crimp. On the court, it has great touch and comfort. Spin control also comes very easily, as there is plenty of bite.” 5.0 male all-court player using Wilson nSix One (68 Holes) strung at 53 pounds LO (Wilson NXT Tour 17)

“I am impressed by the rare combination of comfort and control. Off center hits have very little shock. The tension stays consistent, despite many hours of hard hitting.” 5.0 male serve-and-volleyer using Wilson nPro strung at 60 pounds LO (Wilson Reaction )

“This string has a surprising amount of spin and power. Initially, it plays too stiff, but the comfort level goes up after the first session.” 3.5 female all-court player using Prince O3 Tour OS strung at 60 pounds CP (Prince Tournament Poly 16)

“This string does not have a ton of power. Even though it has a soft, semi-muted feel, the response is still pretty crisp. It is recommended to players looking for a control string in a slightly more comfortable package.” 4.5 male all-court player using Wilson H Tour strung at 58 pounds CP (Babolat Attraction 16)

“This is an arm friendly string with a solid feel. Spin and touch are adequate. Power is on the low end.” 4.5 male all-court player using Wilson KFour strung at 54 pounds LO (Wilson Sensation 16)

“This string feels great initially, but it eventually loses resilience and playability suffers.” 5.5 male all-court player using Wilson nTour Two strung at 55 pounds CP (Wilson Ultra Synthetic Gut 16)

“Strings move on spin shots. Holds tension very well. Plays stiff.” 4.5 male baseliner with moderate spin using Prince O3 Hybrid Spectrum MP strung at 60 pounds LO (Tecnifibre NRG2 17)

“This strings starts with a stiff feel, but it softens over time. The control and spin are average. Durability is impressive.” 6.0 male all-court player using Prince Hybrid Spectrum MP strung at 60 pounds CP (Prince Premier w/Softflex 16)

“This string has a firm feeling without being overly harsh.” 4.5 male all-court player using Wilson KPro Open strung at 62 pounds LO (Luxilon Timo 18)

“Initially, this string has a great feel. Touch shots and lobs are very easy to measure. After several hours of hard hitting, it starts to go dead and control suffers.” 5.5 male baseliner with heavy spin using Head MicroGEL Prestige Mid strung at 64 pounds CP (Kirschbaum Super Smash Spiky 16)

“This string makes a slight ‘twang’ sound. Off center shots lack power and control.” 5.5 male all-court player using Head Liquidmetal Radical OS strung at 65 pounds CP (Babolat VS Touch 16L)

“The ball seems to slide of the strings, making it hard to control the depth and trajectory with spin.” 5.0 male all-court player using Prince Extender Thunder 880 OS strung at 48 pounds CP (Prince Synthetic Gut Original 17)

“As a Kevlar user, I have trouble getting control from such a springy string.” 3.5 male all-court player using Prince O3 Blue strung at 63 pounds CP (Kevlar 19)

(Strings normally used by testers are indicated in parentheses.)

Playtester ratings

EASE OF STRINGING (compared to other strings)
much easier	1
somewhat easier	8
about as easy	22
not quite as easy	4
not nearly as easy	0
OVERALL PLAYABILITY (compared to the string played most often)
much better	0
somewhat better	6
about as playable	14
not quite as playable	13
not nearly as playable	2
OVERALL DURABILITY (compared to other strings of similar gauge)
much better	0
somewhat better	9
about as durable	22
not quite as durable	4
not nearly as durable	0
RATING AVERAGES From 1 to 5 (best)
Playability	3.4
Durability	3.5
Power	3.3
Control	3.3
Comfort	3.3
Touch/Feel	3.2
Spin Potential	3.3
Holding Tension	3.4
Resistance to Movement	3.4

See all articles by Greg Raven

About the Author

Greg Raven  is an associate editor for Tennis Industry magazine and technical writer. He is certified as a Master Racquet Technician by the U.S. Racquet Stringers Association. He can be reached via e-mail at greg@usrsa.com, or through Facebook, LinkedIn, and Twitter. He plays tennis three to five days a week, and is turning into an avid cyclist.

From the January 2009 issue
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