Tennis Industry magazine


Playtest: Wilson NXT OS 16L

By Greg Raven

Wilson NXT OS

Wilson NXT OS is the newest edition to the NXT family of strings. Wilson tells us it specifically engineered this multifilament, polyurethane-impregnated string for oversize and super oversized rackets. Wilson’s goal was for NXT OS to retain tension longer than other premium performance strings, while maintaining the feel, larger sweet spot, and reduced shock of other strings in the NXT line.

The construction of NXT OS begins with a copolymer micro-core. This micro-core is wrapped with five pre-stretched thermal-set bundles of high crystallinity Xycro micro-fibers. During thermal-setting the fibers are heated and stretched, and the bundles remain stretched while cooling. According to Wilson, this takes some elongation out of the string and allows the string to retain tension longer once installed. In Wilson’s lab tests, NXT OS maintained tension 24 percent better than other premium performance strings.

For added durability, copolymer monofilament “abrasion shields” surround each of the five pre-stretched bundles.

NXT OS is available in 16L in white only. It is priced from $15 for coils of 45 feet. For more information or to order, contact Wilson at 773-714-6400, or visit


The coil measured 44 feet, 9 inches. The diameter measured 1.34-1.35 mm prior to stringing, and 1.27 mm after stringing. We recorded a stringbed stiffness of 72 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 69 RDC units, representing a 4 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. NXT OS added 16 grams to the weight of our unstrung frame.

The string was tested for five weeks by 36 USRSA playtesters, with NTRP ratings from 3.5 to 5.5. These are blind tests, with playtesters receiving unmarked strings in unmarked packages. Average number of hours playtested was 25.2.

Most of our playtesters thought that NXT OS was easy to string, although some found it had a tendency to kink. This seemed odd until we experimented a little ourselves. In an open-pattern racquet strung two-piece, NXT OS was indeed easy to install. In a dense-pattern racquet strung one-piece using a box pattern, NXT OS wanted to twist and kink on just about every cross, despite the fact that it has low coil memory. If you are accustomed to installing natural gut, this is no problem, and NXT OS may be a good string for training to use gut. If you are used to installing some of the more invincible-feeling synthetics, however, you may have to slow down a bit when installing NXT OS. NXT OS is soft enough that the end can become mushy during weaving or when negotiating blocked holes. However, it has enough stiffness that a quick trim restores it.

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


Wilson NXT OS tested extremely well. Not only did half of our playtesters tell us it played better than their favorite string, they also awarded NXT OS the top Playability rating of all the strings we’ve ever playtested, compared against other strings in general. NXT OS took second place for Control, tied for second place for Power, tied for second place for Spin Potential, and tied for third for Comfort. As if that is not enough, NXT OS garnered ratings well above average for Durability, Touch/Feel, Holding Tension, and Resistance to Movement. These scores were good enough to earn NXT OS a tie for first place in all-time average scores of all the strings we’ve playtested.

Four playtesters broke the sample during play, one each at five, 12, 25, and 78 hours.


Given the response from our playtesters, Wilson has a hit on their hands with NXT OS, and three-quarters of our playtesters were not even in Wilson’s target audience for this string. The extra length alone should be appealing to some, but we would not be surprised to find out that players with midsize and mid-plus racquets were using NXT OS for it’s many other qualities.


“I love it!” 5.0 male serve and volleyer using Head i.x16 strung at 64 pounds LO (Head Intellistring 16)

“A very good string with gut-like playability. Easy on the arm. Much like Wilson NXT but holds tension better. An ease to string. I would play with this string.” 4.0 male baseliner with moderate spin using Prince Bandit OS strung at 64/62 pounds LO (Volkl Power-Fiber 17)

“I liked this string right from the start. First of all it is very easy to string. Second I can feel the ball very well and have great control. Third it has great ball speed. In my opinion this is a great string. Please let me know the name of the string when it is released.” 5.5 male all court player using Head Liquidmetal Instinct strung at 60 pounds CP (Head Intellistring 16/17)

“Average coil memory, easy to tie knots, less burn than polys, no slipping through clamps, and an RDC stringbed stiffness reading of 70 immediately after stringing. I love this string. I want this string. How do I find out what this is? Some irregularity in the string texture. Surprisingly, after two weeks the Stringmeter still reads 55 on average across the six center mains. Wow!” 3.5 male baseliner with moderate spin using Head i.x3 MP strung at 55 pounds CP (Tecnifibre Spinfire 17)

“This is a good-playing string that maintains its tension very well. It plays well in the cold temperatures we’ve experienced here the last three weeks. I would definitely carry this string as long as it’s reasonably priced.” 4.5 male all court player using Wilson Triad 4 strung at 60 pounds CP (Gamma Professional 17)

“I like this string. It seems like quality stuff. After about two hours hitting with it I did wish I had another couple pounds on the tension. Control was good but I had to cut down on my swing a bit. Plenty of power. I did not like the heavy oily coating on the string. If I need lube, I don’t mind waxing the string. Nice feel also. It feels easy on my arm.” 3.5 male all court player using Volkl V1 strung at 62 pounds LO (Wilson NXT Tour 17)

“Good string! Plenty of control but still almost as much power as my usual string. It plays very hard but I still like it. Very little notching, almost no string movement.” 4.0 male all court player using Wilson Hyper Pro Staff Surge 5.1 strung at 56/54 pounds CP (Gamma LiveWire 17)

“I enjoyed this string. It seems to cup the ball on the strings well. The strings move a minimal amount. If I was playing in a tournament, I would use this string.” 5.0 male all court player using Wilson Pro Staff 7.1 strung at 59 pounds CP (Gamma TNT2 16)

“This string really sets up during the first two hours of play. It is very much like the gut I use, with little or no string movement. It has stayed lively, and I would consider using it in place of gut due to its feel and durability.” 3.5 male all court player using Head Liquidmetal Radical OS strung at 65 pounds CP (Pacific gut 16)

“I am very positively impressed with this string from the perspectives both of stringing and playing. It is exceptionally easy to install, no difficulty with coil memory or friction on the crosses. Overall playability is very good, but the most appealing characteristics are superior tension holding, resistance to movement, and durability (I see no notching or fraying).” 4.5 male all court player using Fischer Pro Impact FT strung at 53 pounds LO (Gamma LiveWire 17)

“The two categories in which this string really excels are power and control. It also excels in another category not mentioned too often, and that’s sound: It sounds good. I am eager to know what it is and the cost. I would definitely consider using it regularly and adding it to my inventory.” 4.0 male baseliner with heavy spin using Wilson Hyper Hammer 4.3 OS strung at 64 pounds LO (Luxilon Alu Power / Gamma syn 16L/18)

“This sample really reminds me of a standard Tecnifibre string. Althought this is a 16 gauge, it is quite lively and playable. The stand-out characteristics about this string are that it’s very soft (good on the elbow), it is great on finesse shots (drop shots, stop volleys, etc.), it’s very playable, and it’s lively with some good pop to it.” 4.5 male all court player using Wilson Hammer 5.2 strung at 62 pounds LO (Tecnifibre NRG2 18)

“Soft, somewhat mushy feeling. Fairly powerful. Once I got used to the feel, this multifilament played well. I think this is a fine, well-rounded string. I hope the price is reasonable.” 4.0 male all court player using Volkl Tour 9 strung at 63 pounds (Pacific Classic Gut 17L)

“This string has a solid feel with good power. It holds tension well. Nice overall playability with above-average durability. Easy to string. It started notching after about 16 hours. Please send me the name of this string.” 4.5 male all court player using Wilson Triad 6.0 strung at 65 pounds CP (Luxilon Alu Power 16L)

“This string is comparable to my normal string. Installing it was easy and it plays on the softer side, which of course makes it more playable and gives it more feel. I like the natural color. Overall a decent string.” 5.0 male all court player using Prince More Performance Balance 950 S MP strung at 60 pounds CP (Prince Powerglide 16)

“The clamps leave white marks on this string. Cutting is easy, and tapered ends last. Stringing through blocked holes is easy with the lubrication. The coating is resistant to notching when pulling the crosses, and remains comfortable pliable. The string does not elongate much during stringing, so it’s important to measure accurately. The string does tend to kink when pulling the crosses. It is difficult to apply stencil ink, and the ink doesn’t seem to soak in very well. The cross strings retain their position when straightened during stringing. On court, the stringbed feels stiff, and the strings retain their position very well. Tension drop-off is more than I expected, to the point that after 15 hours it became difficult to play with this sample. Up until then, the string performed well with crisp volleys and good touch. The stiffness translates to less comfort, but the performance is always assured.” 4.5 male serve and volleyer using Wilson Hyper Hammer 2.3 strung at 63 pounds LO (Wilson Sensation 16)

“The string seemed dry, and I noticed minor friction burn. In play, this string has almost a “dead” quality to it. There is virtually no trampoline effect. The player has to generate the power himself. This is fine for players who want a lot of control. I liked this string overall. It seemed to maintain its tension well over the play period and was pretty durable.” 4.5 male serve and volleyer using Pro Kennex Kinetic 5G Pro strung at 63 pounds LO (Gamma LiveWire XP 16)

“I play pretty aggressively, with a lot of topspin on my groundstrokes. This string moves around, and is starting to notch. It is a very good string, however. It reminds me of Wilson Sensation and Tecnifibre 515.” 5.09 male all court player using Wilson Pro Staff Surge 5.1 strung at 60 pounds LO (Wilson PolyLast 17)

“This string is pretty good, but it feels stiffer than my normal string.” 4.5 male all court player using Babolat Pure Control Zylon 360 strung at 60 pounds LO (Gamma LiveWire XP 16)

“I like this string for a softer string. It seems to hold its tension well. Even though I hit a lot of spin it’s holding up well with no fraying, and minimal notching.” 5.0 male all court player using Prince Attack 1050 strung at 62 pounds CP (Prince Lightning XX 16)

“This string is easy to install compared to the poly I usually use. It has a nice feel to it. I see a little more string movement than I’m used to. I am able to make some great touch shots and drop volleys. It also offers great control for my baseline game.” 5.0 male all court player using Dunlop Revelation Tour Pro strung at 66 pounds LO (Luxilon 16)

“This string was not especially comfortable and did not offer much touch/feel initially, but after playing a couple hours, the overall playability increased. I like how the string does not move very much and allows for good spin potential. Overall, this string helps create an enjoyable tennis experience.” 4.5 male touch player using Prince AirDrive MP strung at 59 pounds LO (Wilson Stamina Spin 15L)

“Very durable. Tension drop is minor.” 4.5 male all court player using Prince More Performance Control DB 800 MP strung at 60 pounds CP (Prince Lightning XX 16)

“During installation this string had lots of coil memory and wanted to coil into snarls. On court, it is a very comfortable string with characteristics much like Tecnifibre NRG. The comfort level makes up for the stringing difficulty.” 3.5 male all court player using Volkl Catapult 3 strung at 50/48 pounds LO (Forten Dynamix 16)

“Not too bad. Pretty nice playability and feel. Does not grab the ball as much as I like. Very good with control and easy on the arm (good after-shock/vibration dampening). Overall a nice, comfortable string with a predictable response.” 5.0 male touch player using Dunlop 300G strung at 62 pounds LO (Luxilon Big Banger 16)

“This strung up extremely easily. No coil memory! I do not hit with lots of topspin, and with my racquet’s dense string pattern, strings last a pretty long time. I am used to playing with a little more comfortable and thinner string. For my style of play, I would not choose this string.” 5.0 female all court player using Head i.prestige MP strung at 58 pounds CP (Klip Scorcher 17)

“The test string is thicker than my normal 16-gauge string, so I probably should have strung it lower than normal. The stringbed felt stiff, lacking touch or feel, but it did play much better as time went on.” 4.0 male all court player using Head Classic MP strung at 57 pounds (Alpha Gut 2000 16)

“Feels like a Tecnifibre string. Soft playing.” 5.5 male all court player using Wilson Pro Staff 6.1 95 strung at 55 pounds (Wilson NXT 16)

“Good feel from the string while playing. Did fray a bit and didn’t hold as tight as my normal string, but for the type of string I feel that this is normal.” 3.5 male all court player using Babolat Pure Control strung at 55 pounds LO (Prince Syn Gut 16)

“This string began notching after 30 minutes, but it did not progress as quickly as my normal string. At the end of the string’s life it held together longer than it seemed it should. At hour four I was certain it would break, but it held out for another hour.” 5.0 male baseliner with heavy spin using Dunlop 300G strung at 70 pounds CP (Gamma TNT Pro Plus 16)

“The string feels stiff and boardy for the first half hour. After that they seem to loosen up and play and feel really improves. It is as though the sweet spot on the racquet expands once the strings break in. I would consider using this string if it came in a 17 or 18 gauge.” 4.5 male all court player using Head i.prestige MP strung at 57 pounds CP (Prince Syn Gut w/Duraflex 17)

“Even with all the dirt on the court, this string is holding up with no fraying.” 4.0 male all court player using Wilson Hyper Hammer 5.2 strung at 58 pounds CP (Laserfiber Tour 16)

“The sample was easy to string, although it was so soft that I had a problem with blocked holes. It handles very similarly to polyurethane multifilaments such as Tecnifibre NRG. On court, the feel was slightly muted and it lacked the crispness I like in a string. Comfort and spin were its strong points, but in other areas it was average or below. The strings started to move after three or four hours, and lost significant tension after eight hours or so.” 4.0 male all court player using Dunlop 300G strung at 58 pounds CP (Babolat Tonic 16)

“For a multifilament, I felt this string to be below the level of other multis that I’ve used. It had a very harsh and stiff feel right after restringing, another odd characteristic.” 5.0 male baseliner with moderate spin using Wilson Pro Staff ROK strung at 60 pounds LO (Wilson Extreme 16)

“I played mostly in colder weather so the strings may have had less feel.” 5.5 male serve and volleyer using Head Liquidmetal Radical MP strung at 60 pounds LO (Prince Syn Gut w/Duraflex 16)

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

Playtester ratings

(compared to other strings)
much easier 3
somewhat easier 9
about as easy 21
not quite as easy 3
not nearly as easy 0
(compared to the string played most often)
much better 2
somewhat better 14
about as playable 9
not quite as playable 10
not nearly as playable 1
(compared to other strings of similar gauge)
much better 5
somewhat better 11
about as durable 18
not quite as durable 2
not nearly as durable 0
RATING AVERAGES From 1 to 5 (best)
Playability 4.1
Durability 3.8
Power 3.6
Control 3.8
Comfort 3.7
Touch/Feel 3.5
Spin Potential 3.5
Holding Tension 3.5
Resistance to Movement 3.6

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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, or through Facebook, LinkedIn, and Twitter. He plays tennis three to five days a week, and is turning into an avid cyclist.



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