Tennis Industry magazine


Playtest: Gosen Sidewinder

By Greg Raven

Gosen Sidewinder is new geometric monofilament polyester string that is made from high–tech polyester resin combined with a chemical additive to increase power, control, and spin. Gosen tells us that Sidewinder utilizes the latest innovation in co-polyester technology. The “Sidewinder” appellation means it is extruded with a rectangular shape and then twisted, providing a string with maximum return of energy from the string to the ball and massive amounts of spin. Gosen designed Sidewinder for advanced players looking for a powerful poly that provides extra spin performance and power.

Sidewinder is available in 17-gauge (1.22mm-1.24mm) in yellow and in black, and in 16-gauge (1.30mm-1.32mm) in orange. It is priced from $13.50 for sets of 40 feet, and $155 in reels of 660 feet. For more information or to order, contact Sportmode at 714-379-7400, or visit sportmode.


We tested the 17-gauge Sidewinder in black. The coil measured 40 feet. The diameter measured 1.24-1.21 mm prior to stringing, and 1.16-1.19 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 x 18 pattern) on a constant-pull machine.

After 24 hours (no playing), stringbed stiffness measured 68 RDC units, representing an 8 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. In lab testing, Prince Synthetic Gut Original has a stiffness of 217 and a tension loss of 11.67 pounds, while Gosen Sidewinder 17 has a stiffness of 221 and a tension loss of 21.26 pounds. Sidewinder added 16 grams to the weight of our unstrung frame.

The string was tested for five weeks by 32 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 28.1.

Gosen Sidewinder has a surface appearance that lets you know right off the bat that it isn’t a typical cylindrical string, although it feels more like a textured string than a geometric. It also seems thick, with 17-gauge Sidewinder feeling more like a 16-gauge string. On our electronic machine, the tension head didn’t stop abruptly on reaching reference tension, but rather eased up to the final tension as the string stretched more than poly strings normally do. Even with its shape, Sidewinder crosses seemed to glide across the mains: It’s no surprise that our playtesters rated it highly in Resistance to Movement. We found installing Gosen Sidewinder very easy for a polyester string.

One member of the playtest team broke the sample during stringing, four reported problems with coil memory, one reported problems tying knots, and none reported friction burn.


Gosen Sidewinder lived up to its name. Our playtest team rated Sidewinder the 9th best string for Spin Potential of the 166 strings we’ve playtested to date for publication. As mentioned above, Sidewinder also garnered excellent ratings for Resistance to Movement, often a key component for generating spin. Sidewinder also ranked well above average in Durability, Playability, and Power, placing it well above average in the overall rankings, too.

Three playtesters broke the sample during the playtest period, one each at 10, 12, and 15 hours.


Despite its high rating for Spin Potential, Gosen Sidewinder’s “gentle” exterior makes it a pleasure to install. Due to its textured-yet-slippery exterior, Sidewinder is an obvious candidate for those looking for a poly to include in a hybrid string bed. You won’t need to worry about tearing up your soft nylon or natural gut when mixing it with Sidewinder.    

Playtester comments

“This one proves that durability strings have come a long way. In addition to the incredible spin and control, this string has great all around playability.” 5.5 male baseliner with moderate spin using Wilson BLX Pro Staff Six One strung at 65 pounds CP (Luxilon Savage 16)

“Impressive comfort and power for such a firm string. Control and spin are amazing. The playability makes it suitable for more than just big hitters. My opponents even commented on the increased speed and depth of my shots.” 4.0 male all court player using Volkl Tour 10 MP strung at 58 pounds CP (Gamma TNT2 17)

“Truly exceptional combination of spin and feel. On big swings the feedback is just right. I feel like I have heightened sense of the ball. Volleys come off firm and comfortable.” 4.0 male baseliner with heavy spin using Prince Triple Threat Hornet strung at 60 pounds CP (Tecnifibre Black Code 17)

“This plays like some of the best polyesters on the market. It handles stiff, but plays quite lively on big swings. The spin is very pronounced. I find it easy to get in a groove from the baseline. If this is priced right, this could be my new string.” 4.5 male all court player using Wilson K Six One (18x20) strung at 60 pounds LO (Babolat RPM Blast/Wilson NXT 16/17)

“As someone who prefers nylon multifilament strings, I find this poly very playable. Spin comes easy. The response off the stringbed is extremely predictable, which keeps me from decelerating in the hitting zone. I would recommend this one to players who make their own power, but who want a little more comfort and control.” 4.5 male all court player using Babolat Pure Drive strung at 52 pounds CP (Gamma Live Wire XP 17)

“This string plays incredibly right off the stringer. I am very impressed by the balance of power and control. Excellent comfort and touch for a poly. This might be my new string.” 4.0 male all court player using Head Youtek Six Star strung at 48 pounds CP (Gamma Zo Black Ice 18)

“This string is firm and crisp. Volleys feel very solid. Strung at 48 pounds, the response on off-center hits has low shock. Big swings from the baseline have exceptional control. This string makes it easier for me to play aggressive tennis.” 5.0 male all court player using Prince EXO3 Tour (16x18) strung at 48 pounds LO (Luxilon Adrenaline 16)

“Good spin and power. The thinner gauge provides added feel. Great for high level doubles, especially when you want to serve wide kickers or hard slices.” 4.0 male all court player using Wilson BLX Six One (16x18) strung at 55 pounds CP (Wilson NXT 16)

“This is a very playable poly with great control. It performs well even on slower swing speeds. Tension maintenance is exceptional. Power is above average for a stiffer string.” 6.0 male serve-and-volley player using Yonex V Core strung at 65 pounds CP (Yonex Cyber Brid 17)

“After the first few hits, the playability and power get better. Control and the durability are the standout features. Players who prefer soft and powerful strings will likely want to hybrid this one.” 4.5 male baseliner with heavy spin using Head MicroGEL Extreme Team Oversize strung at 55 pounds LO (Wilson Sensation 16)

“During the first few hours this string plays a little too stiff and underpowered, but spin is good. After a while, it softens up and plays with more comfort and power. At this point the shots flow with ease.” 4.5 male baseliner with heavy spin using Donnay Dual Gold strung at 54 pounds CP (Tourna Big Hitter Rough 17)

“Excellent control on long, fast strokes. Strung in the mid forties, the trajectory is surprisingly predictable and easy to manage. Players who want great control but prefer a softer feel can lower the tension without drastically distorting the response.” 4.5 male all court player using Wilson BLX Six One Tour strung at 45 pounds LO (Luxilon Alu Power/Wilson NXT 16L/16)

“Spin potential is not only great right off the stringer, it doesn’t waiver over time. This string has a very solid feel. Tension loss is noticeable by the end of the second week, but playability doesn’t go down.” 4.5 male baseliner with heavy spin using Head Youtek Speed MP (18x20) strung at 54 pounds CP (Head Sonic Pro 17)

“The playability and spin are high, but this one is not very lively. The exceptional directional control made hitting passing shots easier.” 5.0 male all court player using Dunlop Biomimetic 400 Tour strung at 50 pounds CP (Dunlop Black Widow 18)

“Very little string movement. Hitting spin with this string is a blast. Whether it’s topspin from the baseline or a slice approach shot, there is definitely extra bite. The trajectory is very easy to control, which leads to bigger swings and more power. Off-center shots are a little jarring, but not uncomfortable.” 4.0 male all court player using Head MicroGEL Radical Pro strung at 54 pounds LO (Head Intellitour 17)

“I can take a full rip from the baseline without fear that the ball is going to sail long. This allows me to aim closer to the lines. The feel on slow swings is not as dead as most of the polys I’ve hit.” 4.5 male all court player using Wilson nPro strung at 59 pounds LO (Babolat Superfine Play 17)

“Surprisingly high elongation during installation for a poly. This string initially lacks feel, but it eventually improves. The high spin level stays constant over time. The power level is definitely high for a poly, which should make this suitable for a wider range of players. This does not play like a niche poly, aimed exclusively at players who rip the felt off the ball.” 4.5 male all court player using Vantage BC30 strung at 54 pounds CP (Kirschbaum Pro Line No.2 17)

“Installation is easy due to the low coil memory. This is very comfortable for a durability string. Power is moderate. After several weeks it’s still playing well. Recommended to big hitters and string breakers who are looking for more comfort.” 4.5 male baseliner with moderate spin using Head Youtek IG Speed Elite strung at 52 pounds CP (Gosen OG Sheep Micro 16)

“Nice feel for a string that handles so stiff. The extra control gives me more confidence, which results in faster swings and heavier balls. The playability lasted for about two weeks of hard hitting, which is not terrible by any stretch.” 4.5 male all court player using Wilson BLX Khamsin Five FX strung at 55 pounds CP (Wilson Hollow Core Pro 17)

“Excellent spin and control. Decent comfort for a poly.” 3.5 male baseliner with heavy spin using Prince EXO3 Ignite Team strung at 54 pounds CP (Luxilon Adrenaline 16L)

“This string provides good power and durability. The standard tension loss does not seem to affect spin or control, both of which are extremely exceptional. Playability is not bad for a durability string.” 4.0 male all court player using Babolat Pure Storm GT strung at 54 pounds CP (Pacific ATP Hybrid 17)

“This string is a spin monster. With its thinner gauge and textured surface, I feel better able to move the ball around the court. Power is sufficient for a poly, but the comfort slips a little after the expected drop in tension.” 5.5 male all court player using Wilson K Six One (16x18) strung at 53 pounds CP (Luxilon Alu Power 16L)

“Nice pop on serves. Excellent control and spin from the baseline. Power on groundies is not as good as with serves.” 4.5 male all court player using Head Youtek Six Star strung at 55 pounds CP (Head Sonic Pro 17)

“The feel is a little stiff in the beginning, but it settles into a nice crisp response. I find it easier to go on offense with this string. Applying spin on slower strokes does not work quite as well, but that could be a tension issue. On block volleys where the ball isn’t coming in fast, I find it a little harder to achieve depth.” 4.5 male baseliner with moderate spin using Babolat Pure Drive strung at 50 pounds LO (Polyfibre TCS 16)

“While feel isn’t great, this has a good combination of power, spin, and control. You can string this one lower to get a softer response without losing control. I find myself playing with polyester more and more. The market seems to be figuring out how to create more playable polys.” 5.0 male all court player using Wilson BLX Six One Tour strung at 54 pounds LO (Luxilon Alu Power/Wilson NXT 17/17)

“Excellent soft poly. The first six hours are great, but then the string gets hard to play with. After the tension loss, the string plays dead and the ball starts to fly all over the place.” 4.5 male all court player using Wilson BLX Six One Tour strung at 60 pounds CP (Topspin Cyber Flash 17)

“Plays a tad firm, but more comfortable than expected. I get good control when my weight is behind the ball. When I’m on defense or am otherwise late to prepare, the ball lands too short. I would probably hybrid this with a lively cross in order to make it play closer to my regular set-up.” 4.5 male all court player using Wilson K Tour strung at 50 pounds LO (Wilson NXT 16)

“Excellent spin! Decent comfort for a poly. Touch and power are a little lacking. I would probably pre-stretch this one next time in order to combat tension loss. This is a good option for big hitters who do not mind cutting it out after the tension drops.” 4.0 male baseliner with heavy spin using Wilson SledgeHammer 2.6 strung at 61 pounds CP (Natural Gut 16)

“The ball definitely seems to pop off the strings with more juice than other polyesters I’ve used. It is a little tough on the arm. I get great action on slices and topspin. Kickers have more kick. I find it easier to camp on the baseline and swing big with this string. Approach shots are a little harder to control.” 4.5 male all court player using Wilson nSix One (16x18) strung at 59 pounds CP (Klip Legend 16)

“Outstanding spin, but not as forgiving as the softer co-polyesters on the market. The feel is too stiff initially and, consequently, a little hard on the arm. Tension and playability go down noticeably after two weeks of hitting.” 4.5 male baseliner with heavy spin using Babolat Pure Storm Ltd GT strung at 47 pounds LO (Head Sonic Pro 17)

“Control and touch are lacking. I was hoping that the string would improve after the break-in period, but it did not. As a touch player, I would hybrid this one with something with better feel and more responsiveness.” 4.0 male touch player using Donnay Formula strung at 55 pounds LO (Genesis Hexonic 16L)

Playtester ratings

(compared to other strings)
much easier 1
somewhat easier 2
about as easy 22
not quite as easy 7
not nearly as easy 0
(compared to the string played most often)
much better 0
somewhat better 7
about as playable 15
not quite as playable 7
not nearly as playable  2
(compared to other strings of similar gauge)
much better 2
somewhat better 12
about as durable 17
not quite as durable 0
not nearly as durable 0
From 1 to 5 (best)
Playability 3.5
Durability 4.1
Power 3.5
Control 3.5
Comfort 3.1
Touch/Feel 3.0
Spin Potential (9th overall) 3.8
Holding Tension 3.3
Resistance to Movement 4.0

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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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