Tecnifibre X-One Biphase 17 String Red
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A premium multifilament string, X-One BiPhase delivers superb comfort and feel and a crisp response. A good choice for players seeking an arm-friendly string without sacrificing power. Provides good tension maintenance too. About as gut-like as synthetics get. Offers a livelier feel, but with slightly less durability compared to the 16-gauge version and is a great choice to liven up a tight string pattern.

According to Tecnifibre, "the X-One Biphase string uses High Heat Capacity (H2C) fibers which allows the use of an innovative chemical treatment process called Trimerization. This new process increases the cohesion between chemical molecule links through extreme variations in temperature to result in ultimate dynamic efficiency (power) and exceptional feel. The new patented Biphasic process, with its visible marks on the string, extends string life by 20% and offers increased spin. Similar to its leading string, NRG2, the multifilament fibers within this string are immersed in polyurethane to provide shock absorption and optimum comfort."

  • Gauge: 17 / 1.24 mm
  • Length: 40 ft / 12.2 m
  • Construction: Multifilament / Polyurethane / H2C fibers / Biphasic treatment
  • Color: Red
Learning Center

Comments: Been revisiting this string in my new Blade 104 at 48 pounds. It felt better than the Gamma LWP 17g at the same 48 pounds. There seemed to be better feel and more spin on my groundies. My serves definitely felt like they had more pop. It's too bad that the price has gone up about $3 a pack since my posting back in 2012.
From: Mike, 6/15

Comments: What a great string! I have tried it at 52lbs and now at 56lbs. Great at the baseline and for those touch shots at the net. I have an on going tennis elbow problem and this string really helps. Pretty close to gut feel as you are going to get. A very forgiving sting that gives you extra control and enough pop. I have tried all kinds of strings, but this is the best for me right now. If you are looking to try a string and you have elbow problems or you want something close to gut at less then half the price, give it a try.
From: Steve, 11/13

Comments: I have about 7 hours on a full bed of this string strung at 58 lbs in a BLX Blade 98. Fantastic stuff. I love the NRG string, but this is better. Seems more durable, as I noticed the NRG fraying almost immediately and I don't see any of that with the X-one. Great power and good spin. Fantastic feel of the ball in the sweet spot and it seems to love hitting flat forehands on high balls -- really provides great feedback and super easy on the elbow and shoulder, even hitting all out in practice rallies. It's worth the cost to me, but I string it myself. I haven't found price a very good indicator of strings for me, but this stuff is worth the dough. I still doubt it will last long as with most multis, but I don't care -- it's all I am stringing my sticks with in the future.
From: Mike, 10/13

Comments: I used to use the BLX PS 6.1 95 with Babolat Ballistics. If I just push the ball, no tennis elbow. But if I try to add power and really pocket the ball, 5 minutes later the elbow would fight back and I barely would be able to pick up my arm. Then I read many reviews about these and decided my that elbow has reached its limits. When I first tried it out, it was a very cold day. Maybe around 40 degrees. I did have tennis elbow when I was playing, so I was very disappointed. A week later when it was warmer, the tennis elbow was gone. I was smacking every ball. It went in by the baseline, and no tennis elbow during practice. I did notice my arm was a little sore. I did not have to change the way I play for these strings. I did notice I became a lot better. Especially my serves. More consistent and more pop. I did not get as much spin as I did before, but I somewhat kind of like it a little flatter than usual. Get if now if you have major elbow issues.
From: Tommy, 3/13

Comments: I used this string on a Prince Hybrid Air Ignite strung at 58 lbs. My goal was to really push the strings to it's limit while swinging with as much topspin as I'm capable of. I have roughly 7-10 hours worth of hitting divided over 4 days. When I first took the string out, it was pure magic. Hit seemed almost telepathic and the balls would spin straight down with good depth. Around day 4 I felt the performance drop off a little as my shots began to feel harder to control and would occasionally dive passed the baseline. I thought it was my technique or fatigue so I put down the racket for a few days. I came back to hit and felt the same thing. I can definitely say playability decreased after the 7-10 hour mark. Those first 6 hours, however, are downright splendid.
From: PS, 4/12

Comments: Really nice alternative to natural gut. I had a Dunlop 200 4D Tour racquet strung with the 16G version at 60 lbs and a newer racquet (same kind) strung with 17G version at 58 lbs. Both strings are very easy on the arm and offer crisp returns with good control. The 17G version has more power and better spin but less control than the 16G version as strung. Both strings move about (17G much more) and start fraying after about 2 months on but then seem to last for quite a while after that. Did not see much difference in durability between the 16G and 17G as both are shot after about 6 months (playing twice weekly). I play doubles (3.5-4.0 level).
From: Bert, 3/12

Comments: I found this string by doing a Google search for best tennis strings. I have played with it two weeks and it is quite good, especially for the price. I was using the Gamma Live Wire Pro but at $20 a pack, it is costly. This is a much better option so far at $16.
From: Mike, 3/12

Comments: An excellent string for as long as it lasts, seems to fray then notch in less within 3 weeks then has to be replaced prior to breaking. I can't afford to use it.
From: Anon, 12/11

Comments: Advantages of the X1 string is that it has a soft feel to it. I can feel the ball well and it has spin potential and good pop. Disadvantages would be that it breaks easily, and I don't like entire string bed with X-One as it feels like a spring board. I also found it pricey. I like X-One in my crosses with Signum Pro Poly-Plasma on the mains and it works great. I went this route to get a little extra feel on the ball I felt I was missing with Signum Pro Poly-Plasma or Black code strung the entire way. X-One is not very durable so if you are a string breaker and don't string your own racquets I would not recommend unless you have very deep pockets. I am not what I would call a string breaker but I string 3 racquets at a time within 10 days rotating all racquets I will have to string at least one racquet again. I play around 3 days a week and am a 4.5 player.
From: David, 11/11

Comments: I agree with everyone else's reviews. This is an all around type string. I think it is similar to natural gut in terms of feel and touch.
From: Mikel, 10/11

Comments: This is an excellent string. There is tons of power, spin and control. But string starts to fray after first hour. Anyway, this string has become my string of choice. I use a Babolat Drive Z strung at 55 lbs.
From: Gennady, 10/11

Comments: I really love the Tecnifibre X-One Biphase 17 string. It's the best string I've used. I've recently been able to compare this string to NRG2 17. I have two Babolat AeroPro Cortex racquets; one is strung with NRG2 and the other with X-one Biphase 17. Both racquets are strung at 60 lbs. The X-one string is better in many ways. I don't hit with heavy topspin and only generate moderate racquet head speed, but I can definitely see that I have more spin potential with X-one. I also notice that the string gives more control and "effortless" power. I get better net clearance, good depth and I find it easier to move the ball around the court. It gives good feel at the net as well. Also, it's very arm friendly and I can hit with a lot more comfort. When hitting with NRG, I can feel a slight pain returning to my elbow. When comparing X-one Biphase 17 and NRG2 17, X-one is just a bit better in all categories. I play twice a week and the only thing that I don't like about X-One is its durability. Once it starts to fray, it looses some tension and the balls start to fly, a bit.
From: Glenn, 9/11

Comments: I love this string! It is very powerful and has a lot of comfort and feel. It has more comfort and feel than power. But they are all evenly spread out. I have a Head Youtek IG Speed MP 18x20 and I put these strings on it because I am trying out Novak's setup as an experiment. I even have his vibration dampener. These strings are great and I definitely recommend them. They play best around 57 lbs. Great string! But it lacks spin. It has a low spin potential.
From: Anon, 9/11

Comments: Great string! I was a gut user all my tennis life (30 years) and this string is close as I found yet. It is easy on arm and spin and power are there. I use it in my Head Prestige Pro 600 and it is a dream. 3.0-5.5 players can take advantage of the playability of this string.
From: Mark, 9/11

Comments: I have a hybrid of Tecnfibre X-One Biphase and Red Code 17 g at 26 Kg and while I love it, I have to say that it breaks way too quickly. X-One Biphase starts fraying in 3 hours and breaks in 4-5. The Red Code shows no signs of wear whatsoever. I just came back from tennis camp, played about 18 hours and broke strings on all my racquets. If you don't mind the constant purchasing/restringing than you'll love everything about this string, but for me, not durable enough.
From: Adi, 8/11

Comments: I suspect that of all the strings listed on this site with customer feedback attached, the X-One may have generated the most comments and with good reason; this is a very good string! I have a little variety in my game and whether I'm hitting with slice or top-spin from the baseline, making an approach shot or at the net, this string offers an amazing combination of power and control.
From: AJK, 7/11

Comments: My favorite string, bar none. I've tried dozens of others, but none match this string as a whole. It's only weakness is its durability, but it will last you ten hours or more, which isn't bad for a multi. Don't hybrid this string though. It always breaks on the crosses and a polyester in the mains just makes the crosses wear out faster. Don't wait until it breaks to replace it either. Once it begins to fray significantly it quickly begins to lose its control and everything will begin going long. A joy to string as well.
From: Darin, Richland, WA, USA. 5/11

Comments: I was an advocate of the Tecnifibre NRG 17g line. Well after trying this string I am switching. This string provides noticeably more power, control,and spin. The wear has been acceptable. It's a slightly higher price but well worth it.
From: Rich, Bethany Beach, DE, USA. 4/11
NTRP Rating: 4.5

Comments: Too crisp to be a real replacement for gut for me but it feels great to play with; good power and all spins are very easy to generate. Serves felt good, but control on groundstrokes for me wasn't as good as gut, power wasn't too bad either. Strung in a k factor tour 90 at 58lbs in the mains with pro hurricane in the crosses at 55lbs. Much easier to string than gut with none of the panic that accompanies it. Playing in damp or wet conditions doesn't seem to be as big a deal as when using gut either; in my part of the world I'd be stringing 3 times a week if I let my gut get wet and it's simply not practical nor is it financially possible. Gut is simply too expensive. If money was no object then I would be using 17g Babolat vs gut with the pro hurricane I use now, but until then, this will more than suffice.
From: Steven, Scotland, 03/11

Comments:Words cannot describe how great this string is! It's virtually a natural gut at the fraction of the price! I'm a hard hitting all court player so durability is an issue and I found that for a multifilament string it holds up quite nicely, it can last about twenty hours before I need to restring. It wasn't too cost effective as a full bed but once I strung it with the black code on the mains durability, feel, power, and spin were all there!
From: Earl, San Diego, CA, USA, 03/11

Comments: The best multifilament out there!! This string has a great balance of feel, spin, comfort, control and power. I quit using the NXT's and Babolat gut for this string. It's easy to string and the durability is good for a multifilament. I also appreciate it being easy on the body. If you like using a multifilament or gut...this is a must try!! Babolat Aero Pro Drive / Aero Pro Lite Mains 60 / Cross 57.
From: James, Tuscaloosa, AL, USA, 03/11

Comments: The best string I have ever played with. It really improved my weaknesses without harming what I was doing well with my prior string (Luxilon ALU Rough 125). Finally a string that doesn't make you have to compromise. My game simply got better! 4.0 Baseliner.
From: George, Boston, MA, USA, 02/11

Comments: This is my latest string choice, and I have played with it for 1 session. The feel is great; power is decent, red color is so sharp that everybody can see it. This string has the ability to generate heavy spin, but it's not that easy. The surface of string is so smooth; I sometimes find the ball just slip off the string bed in some running shots. I have just tested with it for 2 hours of play; the surface of string is already having some wear. Not sure how long can this string last, I will keep on playing to find it's average durability.
From: Henry, 01/11

Comments: Excellent string! At first I was a bit skeptical about switching from a poly to this multifilament string. To my surprise, it actually felt a lot better given the racquet I use. I found this racquet to have good power as well as control. This string also has more than average bite for a multi, producing good spin. The only downsides of this string is that on hot days the string can get a bit "mushy" and is not as crisp as a poly, but overall well worth the switch. 5.0 All around court player. Head Youtek prestige mp 53lbs.
From: Jaime, Mississauga, ON, Canada, 01/11

Comments: I cannot believe I have been using full polyester set ups this long. After trying this string, I really regret not trying them sooner. I hit the ball pretty flat and these strings were incredible. With minimal effort, I am able to generate amazing power. While there is some loss of control, the feel, comfort and power are worth it.
From: Barrett, KY, USA, 12/10

Comments: The better choice in multifilament in my opinion. I use this string in the 17g version, strung at 61 lbs. on a K Pro Staff 88. Amazing gut-like feel and great for your wallet!!! You get a nice balance of power and control. I also find this string to be less conductive of vibrations. If you do your own string jobs, you can also carefully pre-stretch it and get little tension drop over the life of the string.
From: Romain, Miami, FL, 10/10

Comments: Strung as mains in a Tecnifibre Speedflex 315 with Red Code crosses. I find sufficient power and great spin with these and also good touch. Very soft on my shoulder and easy to string. Tension maintenance has not been an issue. Prefer to string at lower tensions where they pocket the ball nicely. Excellent in a hybrid setup, which also helps with durability. Highly recommended.
From: Jay, Ontario, Canada, 08/10

Comments: This is the BEST STRING ON THE MARKET! PERIOD! You will not be disappointed in this string. It offers excellent control, feel, power when you need it, and I was very surprised at the amount of spin it generates! WOW! However, you must string it 5 to 6lbs LESS than you normally would string your racquet. I don't know why, but after I had my Volkl power bridge mid10 strung at 58lbs. It felt like 63lbs! I thought my stringer strung it wrong, so I had it re-strung again; SAME PROBLEM! So I strung it way low like pro player Marcos Bagdatis at 50lbs. Mains and 46lbs. at crosses. WOW! There's so much more power and control. This set-up feels like 58lbs to me. This string is so good specially for the price, it lasts very long too! Amazing! Best string on the market.
From: Will, CA, USA. 03/10

Comments: Bought for my daughter who plays varsity in high school and strings her own racquets. These strings are expensive but the control/comfort/spin are almost worth it. They were not as durable as I hoped, lasting only 7 days (2 hours per days on the courts). My daughter hits with above average topspin. We are looking for something that plays as well and is more durable though.
From: Anon., 10/09

Comments: Agreed, don't pay attention to the negative comments. People need to pay more attention to the construction of a string and compare it to similar strings. This string seems to work best in mid-size frames that are on the stiffer side like a Wilson Pro Staff 6.1 classic because it opens up the pattern a little more. The string is best comparable to other multi fils like Wilson NXT and NGR. Personally I'll take this string over NXT because its a little firmer feel on ground strokes but also has softer touch on more delicate shots as well as good ball pocketing without TOO SOFT a feel.
From: Joe 4.5, Woodstock, Georgia USA 08/09

Comments: Don't pay attention to the negative reviews. I decided to try the Tecnifibre X-One Biphase 17 string red. From the start a big, big difference. Immediately, I felt the advantages of using this strings. Better feel, better control, more topspin, more power & spin on your serves, holds the tension well & at the same time soft on your arm. Actually, with these new strings, my new racquet became alive. The only thing I didn't like is the durability. I have been playing with the same strings for about three weeks now, but by the way they look, it seems that they only have one to two weeks more to go. So I decided to put on string savers on my next Tecnifibre X-One Biphase 17 string red that I have already bought for my new string job. Go ahead & try this strings, you won't be disappointed by the overall performance & actually it may improve the level of your game.
From: Luis, Edmonton, AB, Canada.

Comments: This string is very GOOD as a hybrid, you just have to use the right poly on the mains otherwise it crashes fast. I used a poly string as a hybrid and almost every shot i hit went in..you'll have to figure out the combination can't let the secret out!
From: Janae, USA. 04/09

Comments: This string is terrible. I'm sad to say that I bought into previous feedback comments of how great a feel it gave and the spin potential, but that was not the case at all. I strung my Tecnifibre TFlash 310 16x19 frames with this string, one at 55lbs tension, the other at maximum (57lbs), but neither felt like I had gained any advantage in terms of power and spin. In fact, I lost some of that desperately needed spin when you hit a ball from an uncomfortable position that somehow has to angle and fall into the court; I'm used to hitting shots like those during matches, but they flew off the court w/ this dull string. The sense for me was that it very much muted the impact of the ball on the racquet and I could not tell whether I'd hit the sweet spot of the racquet or not. I consider myself a baseliner, not afraid to come in to net and able to put away shots, but this string had negative impact on all phases of my game. It needs a lot more liveliness. Anyway, the strings stayed on my frames for 1 week, then I got tired of them.
From: Arnie, Dallas, TX, USA, 10/08

Comments: This is a great string for spin potential. I used it as a hybrid, its really soft. I used this 17g with 16g Pro Hurricane Tour. I definitely felt the extra spin and really livened up my string bed. Also had a lot of feel, I could really tell the difference with my drop shots. I tensioned the x-one with a few more lbs because of the softness of the string.
From: Anthony, MN, USA, 09/08

Comments: This string is simply the best synthetic on the market today. It has the feel of natural gut, but with a little more power and durability.
From: John, Suitland, Maryland, USA. 8/08

Comments: Great string. I use them on the mains and hybrid with Prince Synthetic Gut Duraflex 17g for the crosses. I find that it helps to maintain the feel longer when I sting the synth gut on the crosses 2 lbs tighter. The red and white combo of my hybrid looks great too! I have tried the 18g as well, but only use the 18g for when I am playing in a tournament. The spin is much better as is the overall playability, but the 18g does not last me more than 1 set if I am lucky.
From: Lawrence, Geneva area, Switzerland. 6/08
4.5 aggressive baseliner: frequent string breaker.

Comments: I've been using this string on the Ektelon O3 White for the past several months. I've used tecnifibre before, but went away from it the past couple of years, mainly due to cost. This string is a great all around string. Great power, great control and it seems to last quite a while. The red color just adds to the uniqueness of the string....and goes great with the white racquet.
From: Jeff, Central Cali, USA, 02/08

Comments: Great string gives me a lot of power and feel however loses feel quickly, still great string for good price
From: Okonowo, Washington D.C., USA, 04/07

Comments: Compared to the new Wilson K Gut Pro, this string is fantastic. Both have a tacky feel when freshly strung. Nothing I've tried surpasses the soft, playable feel of X-One Biphase. The more expensive K-gut Pro is crisp, but the soft controlled feel of X-one is superior. I have 16-gauge X-One on my 18X20 Tecnifibre 320. I found no durability issues using the thicker gauge, but I used 17G on my Liquidmetal Rave mains with ALU Rough 16L on the crosses. Great for a 16x19 stringbed for power and control if you don't mind the softer mains being cut by the stiffer poly crosses. I don't know how a hybrid bed would work with the X-One strings unless you use in the crosses. They are very soft and don't hold up in humidity or moist conditions (like gut). X-One Biphase compares favorably with playable Gamma strings like Live Wire 17 and Gamma Professional. All of these strings suffer in durability if you hit with heavy spin. Fraying is evident after just one play with 17 gauge versions. If you're a string breaker, I recommend 16G X-One over all other brands. If you desire the extra feel from 17G, well the Tecnifibre X-one Biphase strings are worth the price at 75% the cost of Gamma Professional or K Gut Pro.
From: Jim, Montgomery, TX, USA. 10/07
NTRP: 3.5

Comments: I love the way the ball feels when I hit using this string. I believe it is perfect for my Wilson nTour 95sq (16x20) strung at 60lbs. I've noticed much more spin on my shots and the part I love the most is the way volley's go where I direct/want them to go like I've never experienced before. It also provides nice power and control blend in this low- medium powered racquet. I've also noticed that I have more control on my lobs when opponents approach the net. I highly recommend this to any player looking for great feel, control, desire for topspin, and laser feel on volleys. I am a 3.5 player comfortable enough at the net, but working toward being an all court player.
From: Mike, Arlington, VA, USA, 09/07

Comments: Every now and then I get this great idea that I should try another string. I catch myself reading reviews or comments and get curious. But every time I go back to Tecnifibre X-One Biphase...I wonder why I strayed away. X-One hits with the right combination of feel, control, power and consistency for me. Some people say it goes dead after a short amount of time. To me it plays better and better right up to the breaking point. Only thing I have against the string is that it plays a little stiff the first hour or two. Gamma Professional is the only string I have played with that might play a bit better...but considering the cost, I'll stay with X-one.
From: Rondall, Glen Burnie, MD, USA. 8/07

Comments:Only problem with this string is it isn't sold in a half set. Have to buy a whole set when using a hybrid. I like the power and pop with this string but with an 18x20 string pattern I could not generate much spin. I would recommend this as a good cross with Babolat hurricane or Wilson Enduro in the mains. This string also starts to fray within 2 hours of play.
From: Dave, Lajolla, CA, USA, 08/07

Comments: I tried this because of all the good feedback that there was, before this I had been using the HEAD FXP POWER 17, this string had much more control, and somewhat more spin. Overall I would recommend this string.
From: Vincent, USA, 06/07

Comments: These are the best strings ever. I play with Ashaway Kevlar 17 gauge tension 57 on mains and changed from synthetic gut to Tecnifiber x-one gauge 17 on crosses. The spin, control, and power at tension 61 on head liquidmetal radical are just amazing. This is the best string in the world right now. Period. No arguments.
From: Hormaz, Saipan, Northern Mariana Islands, 04/07

Comments: I tried these strings with some new Volkl V1 DNX frames. The 17-gauge string or the frame really triggered some very severe tennis elbow. I have always used Tecnifibre strings in the past and used the NRG2 16 gauge with great success. It's been a year and after taking 6 months off my elbow is back to normal. I am going to go back to the NRG2 with the same frame that caused the elbow problems and see if the elbow holds up.
From: John, Temecula, CA, USA, 03/07

Comments: Great string. I love it so much. The only thing I didn't like is the durability. So I decided to put on string savers and try the 16. Must try.
From: Anon, 12/06

Comments: Without a doubt the best synthetic string on the market (and better than some natural gut). I'm a racquet stringer and use to recommend Wilson NXT 17 to my serious playing customers. In the last year from my recommendation they're all playing with Tecnifibre x-one Biphase 17 now and everybody's happy.
From: John, USA. 11/06

Comments: Probably the best string I've used this far along with the Gamma TNT Fusion 19g. Initial feel was okay but after a few hours of hitting it felt great. The only problem with this string was that it didn't last me very long so I don't think I'll use it again due to the price. And just a random bit of info, the strings broke on the crosses for me.
From: Lawrence, Placentia, CA 08/06

Comments: This is by far the best, most "gut-like" string I've ever played with. I played with BDE gut Rally and was happy. In the past I have also tried many that claim "gut-like" feel like Gamma Pro XP, Laserfiber Pro, etc...but nothing seems to come close. I would say that this string even felt better than my favorite natural gut as far as feel, control and power. I hybrid with Luxilon TI-MO as I did in my gut string. Tecnifibre X-One Biphase 17 String just feels better and my control is now awesome.
From: KC, California, USA 07/05

Comments: The best multifilament around for the first 15-20 hours, after which the string becomes slow to react and I feel like I need to push the ball off the strings in mid-stroke. I play a ProStaff 5.0 at 62lbs. Strings typically do not break until about a 30-40 hours and when it does it's always a cross.
From: Nekki, Los Angeles, CA, USA. 04/05

Comments: Great string. More control than NRG2 and better feel. Better than gut in that you don't have to worry about the damp. This string is easier to string than gut. Great string. The best multi out there for feel, great job Tecnifibre.
From: Bill, Alberta, Canada. 10/04

Comments: This string offers great feel, power and control. At half the price of gut with similar characteristics-it's a great buy. String durability suffers with the thinner gauge lasting about a month before fraying. I'm an all court 5.5 player who strings his Head Mid-plus XL i.Prestige between 56 and 62lbs.
From: Damion, Los Angeles, CA, USA. 08/04

Comments: The 16g version is just as good. I would say that the string is stiff/ yet soft when you hit hard. Strings do lock in place. Durability is extremely better than Tecnifibre NRG2. I play two times per week and have had this string for almost two months. I'm almost tempted to say that it's worth the price.
From: mackadilly, Talk Tennis. 4/04

Comments: I thought this string was really nice. Gummy like the original Tecnifibre 515, so the strings locked in place, responsive, powerful enough, great soft feel, big sweetspot, great spin. Suspect the durability might be better than Tecnifibre NRG2, especially since the strings aren't sliding around at my usual tension. Tension maintenance appears to be much better. I did a pre-stretch when stringing.
From: NoBadMojo, aka Ameliaislanded, Talk Tennis. 4/04