Tennis Industry magazine


Playtest: Pacific X-Force 18

By Greg Raven

Pacific X-Force is a “poly-like” monofilament string offering increased power and dampened feel. According to Pacific, although the materials of this string are “in the polyester family,” X-Force is not necessarily a polyester string. X-Force is manufactured using a unique heating process that creates elasticity and power in the string. The material and process are proprietary and patent pending.

Pacific X-Force 18

According to Pacific, X-Force has the durability typical of polyesters and is extremely strong, which makes an 18-gauge possible. X-Force combines the playing characteristics of more lively nylon synthetics with the spin and durability of polyester. Pacific tells us that X-Force has an extremely fast “rebound speed,” which may take some getting used to at first.

Pacific X-Force 18 reel

Pacific is aiming X-Force at competitive players looking for a string with more liveliness and elasticity than typical polyester strings.

Pacific X-Force

X-Force is available in 16L (1.29 mm), 17 (1.24 mm), and 18 (1.19 mm) in transparent orange only. It is priced from $9.99 for sets of 40 feet, and $150 for reels of 220 meters. For more information or to order, contact Pacific at 805-892-5901, via email at, or visit Be sure to read the conclusion for more information about getting a free set to try for yourself.

In the lab

We tested Pacific X-Force 18. The coil measured 43 feet 1 inch. The diameter measured 1.16-1.18 mm prior to stringing, and 1.11-1.13 mm after stringing. We recorded a stringbed stiffness of 73 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 68 RDC units, representing a 7 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. X-Force added 15 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 5.5. These are blind tests, with playtesters receiving unmarked strings in unmarked packages. Average number of hours playtested was 24.

Pacific suggests stringing X-Force four to five pounds lower in tension than the average polyester string, and we passed this recommendation along to our playtest team.

Pacific X-Force 18 at 60x
Pacific X-Force 18 at 60X

Installing X-Force is not as traumatic as some polys, and we had no problems with coil memory, although some of our playtest team did. The smooth surface of the string and the small diameter make for fast stringing, and even tying knots seemed easier than typical polys, possibly again due to the smoothness of the string and the thin gauge.

No playtester broke his sample during stringing, 13 reported problems with coil memory, three reported problems tying knots, and two reported friction burn.

On the court

Pacific X-Force 18’s average score for all categories was well above average, making another strong showing for a “polyester-type” string. If you get better spin with thinner gauge string, X-Force is for you, as our playtest team ranked it fifth-place overall for Spin Potential of the 103 strings we’ve tested to date. Despite the fact that it is an 18-gauge string, our playtesters gave it a top-ten ranking in Durability. You have to wonder what kind of durability you would get with the 16L version.

Our playtest team also gave X-Force 18 a top-ten ranking in the Control category, which is a nice complement to the “well above average” ranking it received in the Power category. X-Force 18 also received “well above average” rankings in Playability and Resistance to Movement, and it even garnered an above-average ranking in Tension Retention.

On average, each playtester put 24 hours of playing time on his set of X-Force 18. One playtester broke his sample, after 21 hours of play.


This is the first 18-gauge poly we’ve tested, and only the third 18-gauge of any type ever. Gratifyingly, X-Force 18 was one of the few strings about which no playtester said he wanted in a thinner gauge.

The high rankings for Spin Potential and Playability are not surprising, as the common perception is that thinner gauge strings are better in these categories. However, the top-ten ranking in Durability is a shocker for an 18-gauge string. For that kind of durability with a thin-gauge string, conventional wisdom says that you have to use an Aramid string. But Aramid strings are typically used only as the main strings in hybrid sets, with a softer (and often thicker) cross string to improve feel and playability. With X-Force 18, our playtesters have shown that you don’t need to hybrid it to get both durability and playability.

If you think that Pacific X-Force might be for you, fill out the coupon to get a free set to try.

Playtester comments

“Excellent quality — would play with it and recommend to all, especially to 4.0 + players. Has a solid, clean feel immediately. Holds tension well.” 4.5 male all court player using Head Prestige Mid strung at 55 pounds LO (Gamma TNT 17)

“This string is great! I like the feel and the pop. The strings respond well to everything, but I like the pop the most. All my balls stayed deep, coaxing many short balls. I like it. Great string.” 5.5 male all court player using Head Flexpoint Radical Team strung at 58 pounds CP (Luxilon Timo/Head Synthetic Gut PPS 18)

“This is one of the best strings I’ve ever tested.” 5.5 male all court player using Prince O3 Hybrid Hornet strung at 60 pounds CP (Aramid hybrid 16)

“String has very few imperfections: good quality control. Some coil memory, but not as bad as other polys. Very resistant to notching when pulling crosses. Stencil ink does not apply easily, but an adequate result can be obtained. Some marking/crushing occurred during clamping. Very little string movement during play and wonderful control. No noticeable tension loss after several hours of play. Care must be taken on outer strings to assure good tie-off tension. It is a good choice for players who like to use spin and power, and it will be especially appreciated by those who require excellent control.” 4.5 male serve-and-volley player using a Wilson Hyper Hammer 2.3 strung at 62 pounds LO (Wilson Sensation 17)

“Very stiff feeling and little power, but spin is easy to generate. The strings don’t move and that is good. Feels like your basic poly.” 4.0 male all court player using Prince Graphite Classic OS strung at 58 pounds CP (Luxilon Alu Power 16L)

“I am quite surprised at how well this string plays. I expected the usual dead poly arm-killing string, but this plays more like my regular string. I’d stock it.” 4.0 male baseline player with moderate spin using Babolat Drive Z Max strung at 51 pounds CP (Signum Pro Poly Plasma 17)

“This softer poly has better comfort than most polys I’ve tried. Fairly lively for a poly. I don’t feel the ball nearly as much on the strings, though. However, I give it a thumbs up due to softer playability and increased liveliness.” 4.5 male all court player using Völkl Quantum 1 Power Boost strung at 44/42 pounds CP (Babolat Fiber Tour 16)

“Lots of comments on the color, which is good.” 5.5 male all court player using Head Flexpoint Radical MP strung at 55 pounds LO (Prince Synthetic Gut with Duraflex 16)

“One of the better polys.” 5.5 male baseline player with heavy spin using Wilson nPS strung at 55 pounds CP (Tenex Hy-Kevlar/nylon 16)

“Nice playing string. I might string the crosses one kilo higher. Real nice bite on the kick serve. Decent feel for touch shots.” 5.0 male serve-and-volley player using Wilson nTour strung at 56 pounds CP (Wilson NXT 16)

“I like the string’s broad appeal: it performed well in a few categories. Although it didn’t break, it was about ready to after 20 hours. I would purchase it at a reasonable price.” 5.0 male all court player using Prince NXT Graphite strung at 60 pounds LO (Babolat Ballistic Polymono 16)

“The string created a crisp stringbed. The ball is lively on all shots in the sweet spot. Spin is not a challenge to create and there is no lack of power. It took a little getting used to, but played well.” 5.0 male all court player using Prince O3 White strung at 58/60 pounds LO (Prince Synthetic Gut with Duraflex 16)

“Nice string. It has good pop on the serve and carries spin nicely. Not quite as good on control as my usual string but plays consistently well. I would recommend it for string breakers if priced well.” 4.0 male baseline player using Wilson nPro Surge X strung at 57 pounds CP (Luxilon Big Banger/Gamma Prodigy 16/18)

“Very good string overall. I like the durability. I liked it better in the beginning, but it lost tension too soon. Other than that, good feel and playability.” 5.5 male all court player using Head Liquidmetal Prestige strung at 62 pounds LO (Prince Synthetic Gut 16)

“I was initially disappointed when opening the pack and noticing it was polyester because I normally don’t like polyester except in hybrids. I was pleasantly surprised, however. The increase in power was noticeable right away. I’ve had a problem lately with depth on my shots, but not with this string. Not the best feel, but great results.” 4.0 male baseline player with heavy spin using Wilson Hyper Hammer 4.3 strung at 64 pounds LO (Tecnifibre X-One Biphase 17)

“Nice pop and control. I really like that it doesn’t move. Attractive color.” 4.5 male all court player using Wilson n5 strung at 70 pounds CP (Luxilon Alu Power 16L)

“Very good spin.” 3.5 male baseline player with heavy spin using Babolat Pure Control strung at 48 pounds CP (Prince Synthetic Gut 16)

“Soft and comfortable at first — thought I was going to like it, but it lost significant tension quickly and moved around a lot. Not much spin or fell. Just an average poly.” 5.0 male serve-and-volley player using a Wilson nSix-One Tour 90 strung at 58 pounds LO (Luxilon Big Banger/Babolat VS Gut 16)

“Looks like gut, behaves like kevlar: very little stretch. However, I find it to be very playable, a little stiffer than my usual string, but exhibiting excellent control, decent touch, and more than adequate power. String movement is minimal, suggesting good durability. I would recommend as a hybrid alternative for better players who are looking for the right combination of durability and playability. Not advisable for those with tennis elbow, wrist, or shoulder issues, and not a great choice for those who require enhanced touch on angles and droppers.” 4.5 male all court player using Pro Kennex Kinetic Pro 5g strung at 63 pounds LO (Gamma Livewire XP 16)

“Average playability compared to my current string. Anticipated more power given the tension decrease, but only average power achieved.” 4.5 male baseline player using Head Flexpoint Prestige Mid strung at 60 pounds CP (Tecnifibre NRG2 18)

“A little stiff. Not a bad string for everyday use, and it’s a good practice racquet string.” 4.5 male all court player using Wilson nPro Surge strung at 58 pounds CP (Poly/nylon 17)

“A very stiff string. Good for young hard hitters, but not very good for recreational players wanting a more responsive string. Has poly characteristics, but on the soft side.” 4.5 male all court player using Wilson n5 strung at 56 pounds CP (Gamma Live Wire Professional 17)

“Could swing away with confidence. Comfort would be enhanced by using a softer cross. Great spin on fast swings. Too firm for finesse shots. Very durable for me.” 5.0 male all court player using Völkl DNX 10 strung at 58 pounds LO (Babolat Attraction 17)

“Very cool looking string, but took extra minutes to string — not able too see the crosses easily. Plays very well — lots of pop and spin. Seemed to be a softer poly. Would like to try with a softer/comfortable cross. I would carry it for hybrids if price was right.” male all court player using Völkl V1 OS strung at 58 pounds LO (Gamma Live Wire Professional 17)

“This sample is very good for spin. Control and durability are above average. The string felt softer and more elastic during stringing and I expected comfort and feel to be better than they are. I am also experiencing more string movement than usual for a poly.” 4.0 male all court player using Völkl V1 Classic strung at 56 pounds CP (Babolat Tonic 16)

“Fairly soft for a poly. Once I got used to the softness, I was able to control the ball well. Would definitely use in a hybrid. Good but not great string.” 4.0 male all court player using Wilson Hyper Pro Staff 6.0 strung at 55 pounds LO (Wilson NXT/Toalson Cyberblade 17)

“A very stiff string with little feel or touch. Would most likely be used as a main, with a thin, playable cross.” 4.5 male serve-and-volley player using Wilson Pro Staff 6.1 Classic strung at 58 pounds CP (Wilson NXT 16)

“Feels better than expected for a stiff polyester. Playability and control appeared to be very good as I got used to it the first week. However, I increasingly began to feel pain in my shoulder whenever I used the test string.” 4.5 male all court player using Head Flexpoint 6 strung at 55 pounds LO (Gamma Live Wire Professional 17)

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


(compared to other strings)
Number of testers who said it was:
much easier 0
somewhat easier 3
about as easy 13
not quite as easy 13
not nearly as easy 3
(compared to string played most often)
Number of testers who said it was:
much better 1
somewhat better 5
about as playable 8
not quite as playable 15
not nearly as playable 3
(compared to other strings of similar gauge)
Number of testers who said it was:
much better 2
somewhat better 20
about as durable 8
not quite as durable 2
not nearly as durable 0
From 1 to 5 (best)
Playability 3.4
Durability 4.3
Power 3.3
Control 3.8
Comfort 2.8
Touch/Feel 2.8
Spin Potential 3.6
Holding Tension 3.3
Resistance to Movement 3.6

See all articles by

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.



TI magazine search

TI magazine categories

TI magazine archives


Movable Type Development by PRO IT Service