String comparison
X-One Biphase vs Power Fiber Pro
Tecnifibre X-One Biphase against Volkl Power Fiber Pro: ratings, specs and which one fits your junior.
The short answer
Both are multifilament strings. X-One Biphase leads on power, comfort and tension hold. Power Fiber Pro leads on control. They score the same for arm friendliness (5/5). Power Fiber Pro costs less per set.
Ratings
Power
Spin
Control
Comfort
Durability
Tension hold
Ratings are on a 1–10 scale. The higher score is in bold when they differ.
Pick X-One Biphase if…
- You want more power (9 vs 7 out of 10)
- You want more comfort (10 vs 8 out of 10)
- You want more tension hold (7 vs 6 out of 10)
- Your player is younger (recommended from age 8 vs 10)
- Best for: players wanting natural gut feel without gut price
- Best for: those with arm issues or tennis elbow
- Best for: flat hitters with slow to medium swing speeds
Pick Power Fiber Pro if…
- You want more control (7 vs 6 out of 10)
- You want to spend less (from $13 vs $18 a set)
- Best for: juniors with arm sensitivity who want control
- Best for: players moving up from a plush multifilament
- Best for: all-court players with full strokes
Specs side by side
| Spec | X-One Biphase | Power Fiber Pro |
|---|---|---|
| Type | Multifilament | Multifilament |
| Construction | High Heat Capacity (H2C) fibers with Biphasic trimerization process and polyurethane immersion | Multilayer polyamide multifilament: thin-fiber core, polymer layer, two layers of thicker fibers and a polymer jacket; firmer polymer than Power Fiber II |
| Gauges | 16, 17, 18 | 15L, 16, 17, 18 |
| Stiffness | Low | Low |
| Set price | $18–22 | $13–15 |
| Reel price | $200–250 | — |
| Arm friendliness | 5/5 · Excellent | 5/5 · Excellent |
| Cost to maintain | 3/5 | 3/5 |
| Recommended from | Age 8 | Age 10 |
| Levels | Beginner, Intermediate, Advanced | Beginner, Intermediate, Advanced |
| Play styles | All court, Serve and volley, Touch player | All court, Touch player, Serve and volley |
| Junior tension | 52-56 lbs for juniors. Holds tension well for a multifilament. | 50-56 lbs for juniors. |
X-One Biphase in short
X-One Biphase is Tecnifibre's premium multifilament that combines their best technologies into a single string. The patented Biphasic process with visible marks extends string life by 20% while the H2C fibers allow extreme temperature treatment during manufacturing. Multifilament fibers are immersed in polyurethane for shock absorption and optimum comfort. Many users say "I've never tried natural gut, but X-One Biphase is what I imagine it would feel like." Easily one of the more powerful multifilaments available with cloud-like comfort even at higher tensions.
Power Fiber Pro in short
Volkl Power Fiber Pro is a firmer, more controlled and more durable version of Power Fiber II. Bigger filaments of a firmer polymer give it more control than a typical soft multifilament, while it still absorbs shock and vibration. Reviewers rate its power and feel above average and its spin below average, and durability reports are mixed. It comes in four gauges and several bright colors.
X-One Biphase vs Power Fiber Pro: quick answers
Which has more spin, X-One Biphase or Power Fiber Pro?
They tie on our spin rating (5/10 each).
Which is more arm-friendly for a junior?
They score the same, 5/5. X-One Biphase is recommended from age 8 and Power Fiber Pro from age 10.
Which lasts longer?
They tie on durability (5/10). Tension maintenance: X-One Biphase 7/10, Power Fiber Pro 6/10.
Which is cheaper?
X-One Biphase costs about $18–22 a set and Power Fiber Pro about $13–15, at typical retail.
The short answer and the "pick if" lists are generated from our ratings and junior data only. Data verified 2025-01 (X-One Biphase) and 2026-10 (Power Fiber Pro).