Tennis Industry magazine


Playtest: Gamma Zo Plus 16L

By Greg Raven


Gamma Zo Plus Gamma Zo Plus is a co-extrusion fiber, which means it is a monofilament comprised of two materials, one in the center and a second that encases or coats the center filament. In Zo Plus, the center is a high elasticity core, which is encased in a wear-resistant surface. This co-polymer alloy is further processed using Gamma’s TNT2 technology. According to Gamma, this combination provides an ultra-playable string for players currently using polyester strings, who want more control and fewer arm problems.

Gamma Zo Plus is available in 16L in white only. It is priced from $18.00 for sets of 40 feet, and $284.00 for reels of 660 feet. For more information or to order, contact Gamma at 800-333-0337, or visit its web site.


The coil measured 40 feet 9 inches. The diameter measured 1.33 mm prior to stringing, and 1.27 mm after stringing. We recorded a stringbed stiffness of 83 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 70 RDC units, representing a 16% 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% tension loss. Gamma Zo Plus added 13.9 grams to the weight of our unstrung frame.


Tested for five weeks by 35 USRSA playtesters, with NTRP ratings from 3.5 to 6. These are blind tests, with playtesters receiving unmarked strings in unmarked packages, to reduce preconceptions and biases regarding manufacturers, type of construction, and materials. Average number of hours playtested was 20.


Gamma recommends reducing tension by 10 percent compared to typical nylons when installing Zo Plus. Zo Plus is fairly easily to install, with little coil memory and a nice supple feel. The suppleness does not, however, impair its ability to negotiate blocked holes. The string also feels clean, and there is no oily or greasy feeling, but on denser string patterns it can be difficult to pull the crosses through. One playtester had a problem with the tension head scarring or tearing the thin wear-resistant coating, leaving the stringbed looking worn even when the string is brand new.

No playtester broke his sample during stringing, three reported problems with coil memory, one reported problems tying knots, and five reported friction burn.


As expected, Zo Plus received above average scores for durability, and 25 out of 29 of our playtesters rated it as being at least as durable as other strings of similar gauge. But our playtesters’ ratings also were well above average for holding tension, which is every bit as important if you want a string that does more than resist breaking. Zo Plus also received ratings well above average for power, and above average for control and resistance to movement. These are also three important categories for a polyester string to score well in. Players are always looking for more power, but they are even more excited when they get both extra power and extra control. Finally, the resistance to movement probably helps Zo Plus to be more durable. Eight playtesters had Zo Plus break during play, four at 3 hours or less, three at around 15 hours, and one at 24 hours.


Polyester strings are continuing to gain popularity, in large part because of their durability. But not everyone likes using polyester strings, and some players who currently use polys would like to have a string with the benefits of a poly but with more comfort. Gamma’s Zo Plus is durable and powerful, holds tension well, offers good control, and resists movement. If you are a USRSA member, Gamma is sending you a free set of Zo Plus to try for yourself. If you haven’t already received it, it should be appearing in your mailbox soon.


“Great playing control string. Very little movement and I saw almost no tension loss. Really enjoyed playing with it.” 4.5 male all court player using Volkl Tour 10 MP strung at 59 pounds CP (Head Intellitour 17)

“This is one of the best test strings I have received. Power is great, comfort is superb, and it has good touch. I would definitely use this string to play and teach with. Got to get some. Great string.” 4.5 male all court player using Wilson H5 strung at 57 pounds LO (Wilson Stamina 16)

“Stringing the mains was very easy without that much coil memory, but I had the hardest time pulling the crosses through the mains. I really enjoyed playing with this string, though. It has great power and control. I would definitely buy this string.” 4.5 male all court player using Wilson Pro Staff 6.1 Stretch strung at 62 pounds LO (Wilson NXT 16)

“This string is above average overall for me. It held tension well and durability was excellent throughout the playtest, which was longer in duration than usual for me due to the cold weather and indoor court time. I was skeptical about lowering the tension the recommended 10 percent, but in the end, the string produced for me with better-than-average control. I typically use a thinner gauge string, so if this string comes in various gauges, I will be pleased. If the price is right, I will offer this string to my clients.” 4.0 male baseliner with moderate spin using Pro Kennex Kinetic Pro 7G strung at 62 pounds LO (Babolat Ballistic PolyMono 17)

“Nice balance between durability and playability.” 3.5 male all court player using Wilson H Tour strung at 53 pounds LO (Wilson NXT Max 15L)

“This is a stiffer string than I am used to, but I liked it. This seems like a durable string that holds tension well. It did string at least 10 percent tighter than normal string.” 5.5 male all court player using Wilson 5.1 Surge strung at 56 pounds CP (Wilson NXT 16 61)

“This string played very well. It was very easy on my shoulder and arm. I would feel comfortable offering this string to players who have arm trouble but also are string breakers.” 5.0 male serve and volleyer using Head Liquidmetal Radical MP strung at 66 pounds LO (Wilson Sensation NXT 17)

“This string performed better than I thought it would. While stringing I thought it would be a very stiff string, but was pleasantly surprised that the string softened and was much more playable than I anticipated. I would recommend this string to string breakers instead of the new polyesters.” 4.0 male serve and volleyer using Volkl Catapult 7 strung at 52 pounds CP (Natural gut 16)

“This string didn’t move at all for the first 40 minutes of continuous hitting. Then my topspin made the cross strings move around a lot. However, they did continue to allow control of the ball. Kick serves and slices had good rotation and I was pleased with the results.” 4.0 male baseliner with heavy spin using Wilson Triad 3.0 strung at 60 pounds LO (Luxilon Big Banger 16)

“Pretty good string. I enjoyed playing with it.” 6.0 male serve and volleyer using Wilson Triad 5 strung at 68 pounds CP (Wilson Stamina 16)

“This string provides good durability and above-average power. Despite the 10 percent tension reduction, the control was very respectable. I would consider purchasing this string if the price is right. My overall impression is favorable.” 5.0 male baseliner with moderate spin using Wilson Hyper Pro Staff 6.1 strung at 54 pounds LO (Wilson Sensation 16)

“Initially, the string felt stiff but after playing with it for about five hours, it became more enjoyable. I would recommend it to my clients who are looking for a durable string.” 3.5 male baseliner with heavy spin using Gosen Carbon Plus strung at 59 pounds LO (Gosen OG Sheep Micro 16)

“This is a decent string. It installs easily and plays well after break-in (about two hours in my case). The recommended tension drop of 10 percent makes the stringbed a bit too trampoline-like. Durability is only fair, and string movement contributes to early notching and breakage. Playability was not much different from other durable nylon strings. This string is fairly kind to my aging arm, and I felt good about the feel and directional control until it broke. This might be good for heavier ‘tweener’ racquets.” 4.0 male all court player using Prince TT Bandit OS strung at 60 pounds LO (Topspin Poly Polar / Prince Syn Gut 16)

“The first hour after stringing the string felt stiff, but it then became more comfortable. The first six hours of play were enjoyable and I had a lot of confidence in the string. It is extremely durable. I noticed notching after 7 hours, and at 11 hours I had excessive string movement and loss of tension.” 3.5 male baseliner with heavy spin using Head i.radical OS strung at 65 pounds LO (Forten Aramid Gear 16)

“String broke after the first session, sitting in my bag overnight. Tons of spin, though.” 4.0 male all court player using Volkl Tour 10 MP strung at 54 pounds CP (Rab Monoflex Hybrid 17L)

“Somewhat of a simple synthetic string. Off center hits produced a clunking noise. Had a nice feel, and volleys felt solid. The crosses moved too much, though. I did not lower the string tension as suggested. I would recommend this to beginning students.” 4.5 female all court player using Wilson Pro Staff Tour 95 strung at 63/60 pounds CP (Alpha MXT syn gut 17)

“Installing this string was easier than most polyesters but not as easy as regular synthetics. It started out stiffer than most synthetics, and started to lose tension after about 8 hours of play. It felt crisp initially but toward the end it started to feel spongy. I didn’t feel as if I was able to put as much spin on some shots as I am used to, maybe that could be rectified with a thinner gauge.” 5.5 male all court player using Head Ti.S5 strung at 60 pounds CP (Wilson Polylast 17)

“This string felt a little hard, but I prefer that to mushy. It began fraying a little, then snapped on a second-serve return.” 5.5 male all court player using Babolat Pure Drive strung at 54 pounds CP (Babolat VS Touch 15L)

“This string feels good and seems responsive. I do not think it had the touch and feel of a premium string. However, it seems quite durable for the amount of feel it did provide. I would recommend it to someone who breaks strings, but does not want to sacrifice feel.” 5.0 male all court player using Wilson Triad Hammer 6.0 strung at 55 pounds LO (Wilson NXT Tour 17)

“This string installed and played like many polyesters in most categories. I like the string I normally use so I would not stock this string unless it was considerably less expensive than other strings.” 4.0 male baseliner with moderate spin using Fischer GDS Take Off 910 FT strung at 62 pounds LO (Luxilon Alu Power 16L)

“The comfort and playability of this string is not that great. In regards to durability, it did not hold up its end of the bargain, as it moved around a lot. It did hold tension well, though.” 5.0 female baseliner with heavy spin using Dunlop 300G strung at 54 pounds CP (Dunlop Max Comfort / Prince Lightning XX 16)

“I broke the string after three hours of play, a first for me, but the string seemed competent until then. Lowering the tension did create a little too much dwell time on the stringbed for my volleys.” 3.5 male serve and volleyer using Fischer Pro No. 1 strung at 58 pounds CP (BDE Rallye 16)

“I think this string would play much better in a thinner gauge.” 5.0 male baseliner with heavy spin using Prince Attack strung at 65 pounds CP (Gamma Power Play 18)

“I didn’t notice any significant difference due to the lower tension recommendation. I thought this string played just below average in most categories. It just did not grab the ball very well, so the areas of comfort, spin, and touch/feel all suffered. It is an okay string for those folks who play with just about anything.” 4.5 male all court player using Wilson Triad 5.0 strung at 56 pounds LO (Gamma Live Wire XP 16)

“This is an ordinary string. While it seems to hold tension and resist movement, it doesn’t offer any power of feel to set it apart from other durable strings. It feels dead.” 5.0 male all court player using Wilson Surge strung at 62 pounds CP (Wilson Sensation 16)

“This string seems to have good spring but it is difficult to control the direction of the ball, possibly because the string doesn’t have much feel. The outer wrapping came off at the intersections fairly quickly.” 5.0 male all court player using Wilson Hyper Pro Staff Tour 90 strung at 54 pounds CP (Wilson Stamina 16)

“Feels like an average string to me. Not very impressive. It notched easily even when I install it the same way I install other strings. Almost feels like a cheap nylon.” 3.5 male all court player using Wilson Pro Staff 6.0 Original strung at 58 pounds CP (Gosen Polylon 17)

“This is perhaps the worst string I have ever used. The string makes a terrible high-pitched ping while being struck with the ball, and the control was awful. I even had a hard time controlling my shots with my beginning level students. I think I shouldn’t have strung this at the looser tension that was recommended. I cut them out after the first day.” 5.0 male all court player using Prince More Game strung at 56 pounds LO (Prince Lightning XX 17)

“I played one hour and taught one hour with this string, and then it broke in the bag afterward. I would not recommend this string.” 5.0 male all court player using Babolat Pure Drive strung at 53 pounds CP (Babolat Xcel 16)

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

Playtester ratings

(compared to other strings)
much easier 0
somewhat easier 5
about as easy 20
not quite as easy 5
not nearly as easy 1
(compared to the string played most often)
much better 1
somewhat better 4
about as playable 7
not quite as playable 15
not nearly as playable 3
(compared to other strings of similar gauge)
much better 1
somewhat better 14
about as durable 9
not quite as durable 4
not nearly as durable 1
Playability 3.1
Durability 3.6
Power 3.5
Control 3.3
Comfort 2.9
Touch/Feel 2.7
Spin Potential 3.1
Holding Tension 3.5
Resistance to Movement 3.3

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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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