Tennis Industry magazine


Playtest: Gamma Zo Pro 16L

By Greg Raven

Gamma Zo Pro is a hybrid set made up of Zo Power for the mains and Live Wire Professional for the crosses. According to Gamma, Zo Power is an ultra playable 16L-gauge polymer alloy featuring Gamma’s TNT2® Technology, for players who prefer greater power with pinpoint control without sacrificing durability or comfort. Gamma Zo Power 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 Power, the center is a high elasticity core, which is encased in a wear-resistant surface.

Gamma Zo Pro
Gamma Zo Pro
Live Wire Professional and Zo Power
Gamma Live Wire Professional and Zo Power

In the crosses, Professional features what Gamma calls Live Wire Multifilament Technology. Professional features an advanced string construction that incorporates 50 percent more iso-elastic fibers, NCP tension fibers for longer tension maintenance, and new PEEK abrasion resistant fibers woven into the outer wraps for enhanced durability. This unique construction, combined with Gamma’s exclusive Advanced Irradiation Process, is said to provide a crisp, solid feel.

Gamma tells us it designed Zo Pro for players looking for a softer feel than is generally found in an all-polyester string bed, but with more durability and stiffness than that generally found in an all-nylon string bed.

Zo Pro is available in 16L/16 in silver/natural. It is priced from $18.50. For more information or to order, contact Gamma at 800-333-0337, or visit Gamma on-line.

In the lab

We tested the 16L/16-gauge Zo Pro. The coils measured 23 feet 5 inches for the mains and 21 feet 11 inches for the crosses. The diameters measured 1.24-1.25 mm for the mains and 1.32-1.34 mm for the crosses prior to stringing, and 1.20-1.22 mm for the mains and 1.27-1.28 mm for the crosses after stringing. We recorded a stringbed stiffness of 66 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 61 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. Zo Pro added 15 grams to the weight of our unstrung frame.

The string was tested for five weeks by 31 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 24.9. We instructed the members of our playtest team to install the “silver” (poly) string in the mains and the “natural-color” (nylon) string in the crosses.

The Zo Power is about as easy to string as other modern polys, and of course, having it only for the mains is very nice. The Gamma Professional is always a pleasure to use, as its flexibility makes it feel nimble when weaving the crosses. Even though the Zo Power is a stiff 16L and the Professional is a supple 16, the Zo Power feels much thinner than the Professional, and this is borne out by the measurements. This difference in gauge impressed some playtesters, who were happy to have thin mains for spin.

No playtester broke a sample during stringing, 11 reported problems with coil memory, 5 reported problems tying knots, and 3 reported friction burn.

On the court

Gamma Zo Pro scored well above average for Durability, Control, and Spin Potential. In fact, Durability rated exceptionally well with our playtesters both compared against other strings of similar gauge, and as an absolute rating. It also scored above average for Playability, Tension Holding, and Resistance to Movement. These ratings seem to indicate that Zo Power and Professional work well together in this configuration. Whatever its other merits, Professional isn’t normally considered a durability string, yet combined with Zo Power, our playtesters gave it high marks in this category. Likewise, playability and tension holding are not normally attributes of a poly, but here Professional complements Zo Power. Zo Pro did receive only average ratings for Power, but this might be a good thing for such a string.

Five members of the team broke Zo Pro during the playtest period, one each after 5, 10, 16, 18, and 25 hours of testing.


Hybrid strings such as Gamma Zo Pro attempt to square the circle by giving players a combination of strings that will stand up to a lot of abuse, while still providing a semblance of playability, comfort, or both. Considering the prima facie difficulties inherent in such an undertaking, it’s a minor miracle that hybrids work as well as they do.

As noted above, Zo Pro did not rate highly in the Power category with our playtest team. This, however, might make Zo Pro the right choice for two disparate target consumers: big hitters, and players using super over-size frames. Each needs durability, control, and (typically) spin from a string. There might be some in these categories who can control a powerful string, but most seem to prefer to provide power via racquet head speed or racquet head size. Gamma Zo Pro allows either of them to do just that.

Playtester comments

“Great String. Mains complement crosses. This string is great. I love the stiff mains and soft crosses. Great combination. I would buy this string. I love that companies are doing hybrids.” 4.5 male all court player using Wilson nPro Surge strung at 59 pounds LO (Wilson Polylast/Wilson Extreme Synthetic Gut 17)

“I like this string very much. The only drawback is the movement of the strings; I had to readjust after each point. However, I liked both the feel and the pop of these strings.” 5.5 male all court player using Head Radical Tour MP strung at 65/62 pounds CP (Luxilon Timo / synthetic gut 18/17)

“Good String. Very reasonable playability.” 5.0 male all court player using Head Instinct strung at 57 pounds LO (Head Synthetic Gut 16)

“I liked this version of the poly/multifilament mix better than a poly/gut mix I tried. The poly really had nice bite — nice and thin; and the multi maintains tension and was nice and soft. Felt like this combo was every bit as good as the gut mixes (for less cost I assume). Perhaps a coating could prevent immediate fraying/peeling.” 5.0 male all court player using Wilson Pro Staff 7.5 strung at 72 pounds LO (Luxilon/VS Tonic 17/16)

“After 33 hours of playing there is absolutely no notching of the mains. The crosses are starting to fray and the end is near. A great string combo; very similar to my set-up. A good string for big hitters.” 3.5 male all court player using Head Liquidmetal Radical OS strung at 56/62 pounds CP (Luxilon Big Banger/Gamma TNT 16)

“Very nice string from the baseline. Great feel on hard groundstrokes. Was able to hit with confidence. A little firm from the rest of the court for my personal preference. Would definitely recommend the string for anyone seeking durability with a strong baseline game.” 3.5 male all court player using Head Liquidmetal Prestige MP strung at 55 pounds LO (Head PPS 17)

“The sample strung up tighter than expected and stayed that way throughout test, never seeming to lose any tension. Spin is excellent, as is slice underspin. I feel I can drive backhand slice approaches better with this string than with any other I’ve tested. Touch and feel shots are still below average as with most poly hybrids. I would string 2-3 lbs lower next time to see if playability would improve without sacrificing the excellent bite.” 4.0 male all court player using Völkl V1 Classic MP strung at 58 pounds CP (BDE Performance 16)

“This hybrid surprised me since I use natural gut normally; but, once I got used it, I really liked it. Great control — able to swing out. The thin poly in the mains was able to generate a fair amount of spin. This string is fairly comfortable since I strung it down 5-6lbs from usual tension. I think this is a very good combination.” 4.0 male all court player using Wilson Hyper Pro Staff 6.0 strung at 55 pounds LO (Babolat VS Natural Gut 17)

“The string provides a very stiff stringbed and the strings do retain location very well, although the pliability of the crosses made the bed a little forgiving. On heavy spin shots the main strings maintain position almost without falter, even with reduced tension, and should be considered by players who like to use prodigious amounts of spin. Unusually, though, the cross strings moved. Because of the rigidity of the stringbed, it provided less comfort than my usual string, but the synthetic gut cross strings certainly helped to provide comfort and control.” 4.5 male serve-and-volleyer using Wilson Hyper Hammer 2.3 OS strung at 66 pounds LO (Wilson Sensation 16)

“Very good string, but it didn’t last as long as I would have liked. Before it broke the tension dropped, and so did performance. Up to that point, though, I really enjoyed playing with this string.” 5.0 male baseliner with heavy spin using Prince NXGraphite Mid strung at 60 pounds LO (Babolat Ballistic Polymono 16)

“Good string for players requiring extra durability. String generates good power, but lower on comfort and feel.” 4.0 male all court player using Head Classic Midplus strung at 62 pounds LO (Head FXP 16)

“Nice string for hybrid users.” 4.5 male all court player using Wilson Triad 6.0 strung at 70 pounds CP (Luxilon Big Banger 16)

“Good durability string for string breakers with the poly mains. The cross strings were soft, giving it a comfortable feel. Overall: nice balance of power and control.” 5.0 male all court player using Wilson nSix-One 95 strung at 60 pounds CP (Prince Synthetic Gut 17)

“This was a very crisp playing string. I felt like I had a lot of control; access to spin was “o.k.” The strings moved too much for my taste, but the crosses were a very nice touch. I feel like this string would be best suited for a denser pattern. I feel there might be too much string movement and breakage in open pattern frames.” 4.0 male all court player using Head I. Radical OS strung at 60 pounds CP (Luxilon ALU Power 16L)

“Better durability than playability, but was a decent playing string. Because of the stiff mains, control was easier to obtain. Power is provided by the player.” 4.5 male all court player using Prince O3 Tour MP strung at 60/63 pounds LO (Prince Synthetic Gut 16)

“Going into the test, I assumed good playability and comfort from this playtest string. To me it was average and not up to par with what I was using, i.e., high gauge multifilament. However, the string held tension well and had great control.” 4.5 male all court player using Head Liquidmetal Prestige Mid strung at 65 pounds LO (Tecnifibre NRG2 18)

“I liked the feel of the strings, good control and softer than other polyesters I’ve used. The crosses fray. Don’t think this string would last my normal 6-8 weeks.” 3.5 male all court player using Völkl V1 OS strung at 60 pounds LO (Gamma Pro 17)

“Durable and comfortable. Lost tension quickly, and the crosses moved more than I’m used to in comparison to one piece sets.” 4.5 male serve-and-volleyer using Wilson Pro Staff 6.0 strung at 59lbs pounds CP (Wilson NXT 16)

“A very firm-playing string with good tension maintenance. Probably not for the touch player; more for a hard hitting topspin baseliner.” 3.5 male baseliner with moderate spin using Prince O3 Blue strung at 60 pounds CP (Babolat Attraction 16)

“On the whole, I like this string and rate it slightly above average, especially for better players who have problems with string breakage. The design—thin mains with thicker crosses—seemed to impart excellent control and spin, as well as power. On the downside, the string did not deliver as much feel as I would like for angled volleys and drop shots. In addition, the string delivered less in the way of shock absorption. Compared to my reference string, I would experience a bit more arm soreness after a match with this string.” 4.5 male all court player using Pro Kennex Kinetic Pro 5g strung at 63 pounds LO (Gamma Livewire XP 16)

“This is a soft string that is easy on the arm. The cross strings moved excessively from the beginning. After approximately 8 hours of play tension loss was noticeable. The string would be best suited to those wanting a soft, durable comfortable string.” 4.5 male all court player using Wilson T3 MP strung at 60 pounds CP (Gamma Professional 17)

“Not quite as good as I thought it would be. Great spin potential and holds tension quite well. Less control than my current string.” 5.5 male all court player using Head Liquidmetal Prestige Mid strung at 62 pounds LO (Prince Synthetic Gut 16)

“Big disappointment compared to the last 3 or 4 strings I’ve tested. It was difficult to leave my regular string to test this one. I kept waiting for it to get better. It never did.” 4.0 male all court player using Wilson HH 4.3 OS strung at 64 pounds LO (Tecnifibre X-One Biphase/Tourna Natural Gut 17)

“Did not like string at all when first started—too stiff and boardy. It did get better after 10 or so hours, but not a string I would use.” 4.0 male all court player using Wilson Pro Staff Surge strung at 56/54 pounds CP (Gamma TNT 18)

“Boring.” 4.5 male serve-and-volleyer using Head Flexpoint 10 strung at 65 pounds LO (Head Perfect Power 16)

“The crosses broke first, and it lost quite a bit of tension through play. The durability of the poly mains doesn’t make a lot of difference when the crosses break first.” 5.0 male baseliner with heavy spin using Wilson nPS 95 strung at 58 pounds CP (Tenex Hy-Kevlar 16)

“This stuff is terrible.” 5.5 male all court player using Wilson nSix-One Tour strung at 58 pounds LO (Gamma Synthetic Gut 16)

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


(compared to other strings)
Number of testers who said it was:
much easier 1
somewhat easier 3
about as easy 22
not quite as easy 5
not nearly as easy 0
(compared to string played most often)
Number of testers who said it was:
much better 1
somewhat better 7
about as playable 5
not quite as playable 14
not nearly as playable 4
(compared to other strings of similar gauge)
Number of testers who said it was:
much better 0
somewhat better 19
about as durable 6
not quite as durable 6
not nearly as durable 0
RATING AVERAGES From 1 to 5 (best)
Playability 3.3
Durability 3.9
Power 3.0
Control 3.6
Comfort 3.1
Touch/Feel 2.7
Spin Potential 3.3
Holding Tension 3.3
Resistance to Movement 3.2

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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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