String comparison
NRG2 vs X-One Biphase
Tecnifibre NRG2 against Tecnifibre X-One Biphase: ratings, specs and which one fits your junior.
The short answer
Both are multifilament strings. NRG2 leads on spin. X-One Biphase leads on control, comfort and tension hold. They score the same for arm friendliness (5/5). NRG2 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 NRG2 if…
- You want more spin (6 vs 5 out of 10)
- You want to spend less (from $14 vs $18 a set)
- Best for: players with arm issues or tennis elbow
- Best for: developing juniors with slow to medium swings
- Best for: doubles players wanting touch on volleys
Pick X-One Biphase if…
- You want more control (6 vs 5 out of 10)
- You want more comfort (10 vs 9 out of 10)
- You want more tension hold (7 vs 6 out of 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
Specs side by side
| Spec | NRG2 | X-One Biphase |
|---|---|---|
| Type | Multifilament | Multifilament |
| Construction | 1,120 Elastyl fibers bonded with flexy polyurethane resin, SPL coating | High Heat Capacity (H2C) fibers with Biphasic trimerization process and polyurethane immersion |
| Gauges | 16, 17 | 16, 17, 18 |
| Stiffness | Low | Low |
| Set price | $14–18 | $18–22 |
| Reel price | $150–180 | $200–250 |
| Arm friendliness | 5/5 · Excellent | 5/5 · Excellent |
| Cost to maintain | 3/5 | 3/5 |
| Recommended from | Age 8 | Age 8 |
| Levels | Beginner, Intermediate | Beginner, Intermediate, Advanced |
| Play styles | All court, Serve and volley, Touch player | All court, Serve and volley, Touch player |
| Junior tension | 52-56 lbs for juniors. | 52-56 lbs for juniors. Holds tension well for a multifilament. |
NRG2 in short
Tecnifibre NRG2 features 1,120 individual Elastyl fibers bonded with polyurethane resin offering 400% elasticity. This gives 12% more power than standard synthetic polyamide strings. The SPL (Silicon Pyrogene Lubritec) coating improves durability and resistance to notching. "Let's not mince words, Tecnifibre NRG2 is powerful" - ideal for players with slow to medium strokes still developing their swings. Playtesters raved about the soft, buttery feel. One of the best tennis strings for tennis elbow.
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.
NRG2 vs X-One Biphase: quick answers
Which has more spin, NRG2 or X-One Biphase?
Tecnifibre NRG2, with a spin rating of 6/10 against 5/10.
Which is more arm-friendly for a junior?
They score the same, 5/5. NRG2 is recommended from age 8 and X-One Biphase from age 8.
Which lasts longer?
They tie on durability (5/10). Tension maintenance: NRG2 6/10, X-One Biphase 7/10.
Which is cheaper?
NRG2 costs about $14–18 a set and X-One Biphase about $18–22, at typical retail.
The short answer and the "pick if" lists are generated from our ratings and junior data only. Data verified 2025-01 (NRG2) and 2025-01 (X-One Biphase).