Tecnifibre X-One Biphase is a premium multifilament tennis string designed to combine high power, comfort and crisper control than Tecnifibre NRG2. It sits at the top of Tecnifibre’s conventional multifilament range and is positioned as a synthetic alternative for players attracted to natural-gut performance.
Its construction blends 50 percent Elastyl fibers with 50 percent H2C high-temperature fibers. The bundle is impregnated with PU 400 polyurethane, then treated with Tecnifibre’s Biphase pre-stretch process and a smooth SPL finish.
X-One Biphase targets all-court players, doubles specialists and experienced multifilament users who want premium touch without natural-gut care requirements. It remains powerful and is not intended for frequent string breakers. The Tennis String Finder can help compare it with other materials.
Tecnifibre X-One Biphase Rating
| Category | Rating |
|---|---|
| Power | 9/10 |
| Spin | 6.5/10 |
| Comfort | 8.5/10 |
| Control | 7/10 |
These ratings reflect the broader string market and independent playtesting. X-One Biphase excels in power, comfort and touch, while control and spin are less specialized.
Tecnifibre X-One Biphase Specifications
| Specification | Details |
|---|---|
| String type | Premium multifilament |
| Fiber blend | 50% Elastyl and 50% H2C polyamide fibers |
| Matrix | PU 400 polyurethane impregnation |
| Processing | Biphase pre-stretch treatment |
| Surface | SPL or silicone-based smooth finish |
| Common gauges | 15L / 1.35mm, 16 / 1.30mm, 17 / 1.24mm and 18 / 1.18mm |
| Common colors | Natural, Black and Red, depending on gauge |
| Lengths | Approximately 12m sets and 200m reels |
X-One Biphase is manufactured in France. Gauge, color and reel availability vary by market.
Material and Construction
Half of the main fiber blend uses Elastyl, which Tecnifibre identifies as more elastic than standard polyamide. These fibers contribute rebound and easy power.
The other half uses H2C fibers processed at high temperature. Their role is to add stability and improve tension behavior without eliminating multifilament comfort.
PU 400 polyurethane impregnates the bundle throughout. Tecnifibre describes this grade as highly elastic, allowing the matrix to cushion the fibers and create dynamic pocketing.
The Biphase process pre-stretches the string to improve tension retention and useful life. It leaves a subtle, perceptible surface structure, while the final SPL finish adds smoothness and anti-abrasion protection.
Tecnifibre X-One Biphase Performance
Power
X-One Biphase is very powerful. Independent playtesting placed it among the liveliest premium multifilaments, with easy depth on compact and moderate swings.
Elastyl and PU 400 provide the elastic rebound, while H2C and Biphase processing keep the response slightly more defined than an especially soft power string.
The 18 / 1.18mm version is the most responsive. The 15L and 16 gauges provide greater stability and are more appropriate in open patterns or powerful frames.
Advanced fast swingers may find the launch difficult to control. Gauge selection and modest tension adjustment are preferable to assuming a premium multifilament will behave like polyester.
Power rating: 9/10
Spin
Spin is moderate. The final finish supports smooth movement, and the Biphase surface treatment can increase interaction with the ball, but the string remains a soft round multifilament.
Independent testers generally wanted more spin than their polyester setups provided. The lively launch can also make it harder to swing freely enough to create rotation.
Thinner gauges improve ball interaction and may return more easily while fresh. As fraying and notching develop, the mains can remain displaced.
All-court players can produce effective topspin, slice and kick through technique. Heavy-spin baseliners should prefer polyester or a suitable hybrid.
Spin rating: 6.5/10
Control
X-One Biphase offers reasonable control for such a powerful multifilament. H2C fibers and the Biphase process give it a crisper, more defined response than NRG2.
Independent testing still found control limited by the high power level. Players with compact strokes often benefit, while very fast swingers may need more restrained material.
Touch control is a strength. The combination of pocketing and crisp feedback supports volleys, drop shots and directional placement.
Control can decline as tension drops and strings move. The wear indicator helps identify advanced fraying, but trajectory changes may appear before complete failure.
Control rating: 7/10
Comfort and Feel
Comfort is excellent. The polyurethane-infused multifilament bundle cushions impact and enlarges the forgiving feel of the stringbed.
X-One Biphase feels crisper and slightly firmer than NRG2. Independent testers described it as lively, responsive and comfortable rather than mushy.
This premium feedback is one of its main advantages for all-court play. It combines soft impact with enough definition for touch and net work.
The string is not a substitute for medical advice or a guarantee against injury. Racket stiffness, tension and technique remain part of the complete setup.
Comfort rating: 8.5/10
Durability and Tension Maintenance
X-One Biphase has moderate physical durability. The Biphase process and final finish improve integrity, but the fibers still fray under repeated friction.
Tecnifibre explicitly advises frequent string breakers against the product. The 15L / 1.35mm and 16 / 1.30mm gauges provide the greatest resistance.
Tension maintenance is strong for a multifilament because H2C fibers and pre-stretch processing stabilize the bundle. This advantage should not be exaggerated into natural-gut-level longevity.
Physical resistance is separate from useful playability. Replace the bed when fraying becomes deep, launch changes or strings remain displaced. Tecnifibre treats significant fraying as a visible wear indicator.
Choosing the Right Gauge
The broad gauge range makes X-One Biphase unusually adaptable.
| Gauge | General characteristics |
|---|---|
| 15L / 1.35mm | Maximum resistance, stability and launch control |
| 16 / 1.30mm | Balanced durability, power and touch |
| 17 / 1.24mm | Greater liveliness, pocketing and spin access |
| 18 / 1.18mm | Maximum sensitivity and response, with the least resistance |
The 16 gauge is the safest general choice. Dense patterns and non-breakers can benefit from 17 or 18 gauge, while open patterns may favor 15L.
Full Bed or Hybrid Setup
Full Bed
A full bed maximizes X-One Biphase’s premium touch, power and comfort. It suits all-court players who do not need polyester-level spin control.
The thicker gauges help manage launch and fraying in open patterns.
Tecnifibre X-One Biphase in the Mains With Softer Crosses
X-One Biphase mains preserve its dynamic feel. Natural-gut crosses can improve resilience and tension stability, but this is an expensive arrangement that does not exploit gut’s usual main-string role.
A softer multifilament cross creates an extremely plush setup with limited durability benefit.
Softer Mains With Tecnifibre X-One Biphase in the Crosses
Natural gut mains with X-One Biphase crosses emphasize gut’s resilience while keeping the bed soft. The multifilament cross can notch and restrict movement over time.
X-One Biphase also works beneath polyester mains to add power and comfort. The polyester can saw through the fibers, often making the premium cross the first component to fail.
General Tension Guidance
X-One Biphase can begin near the middle of the racket manufacturer’s recommended nylon range. Its high power means players should not automatically copy a low polyester reference.
Players seeking maximum depth and comfort can move modestly lower. Those needing more control can increase slightly or choose a thicker gauge.
Tecnifibre publishes a broad recommended range for its multifilaments, but individual setup matters more than copying the endpoints. Remain within the frame’s approved range.
Use the Tennis String Tension Calculator to organize gauge, pattern and power variables, then adjust gradually.
Who Should Use Tecnifibre X-One Biphase?
X-One Biphase is best suited to:
- All-court and doubles players seeking premium touch
- Beginners and intermediates who want easy depth
- Experienced players leaving firm polyester
- Users who prefer crisp multifilament feedback
- Players who rarely break strings
- Hybrid users seeking a premium soft component
Who Should Avoid Tecnifibre X-One Biphase?
X-One Biphase is less suitable for:
- Frequent string breakers
- Heavy-spin players seeking shaped-polyester bite
- Advanced hitters who want the lowest-powered launch
- Players who dislike string movement or fraying
- Users seeking the least expensive multifilament
- Anyone expecting natural gut without tradeoffs
Pros and Cons
| Pros | Cons |
|---|---|
| Exceptional power | Limited resistance for heavy breakers |
| Excellent comfort | Spin is moderate |
| Crisp premium multifilament feel | Can be too lively for fast swings |
| H2C fibers support stability | Frays with use |
| Biphase pre-stretch improves tension behavior | Premium price |
| Four useful gauges | Less stable and resilient than natural gut |
Tecnifibre X-One Biphase Compared With Other Strings
X-One Biphase vs Tecnifibre NRG2
Tecnifibre NRG2 uses 100 percent Elastyl microfilaments and feels softer and more power focused. X-One Biphase is crisper and slightly more controlled through H2C fibers and pre-stretch processing.
X-One Biphase vs Tecnifibre Multifeel
Tecnifibre Multifeel uses a firm central core and costs less. X-One Biphase offers more premium power and touch, while Multifeel emphasizes value and control.
X-One Biphase vs Wilson NXT
Wilson NXT provides a similarly premium comfort-and-power profile. Independent testing found close performance, with X-One Biphase offering a distinct crisper feel.
X-One Biphase vs Luxilon Natural Gut
Luxilon Natural Gut uses natural serosa fibers and provides superior resilience and tension stability. X-One Biphase offers synthetic convenience but should not be described as identical.
Final Verdict
Tecnifibre X-One Biphase is a premium multifilament built around power, crisp comfort and touch. Its Elastyl/H2C blend, PU 400 matrix, Biphase pre-stretch and SPL finish create a more defined response than NRG2.
Its limits remain those of a highly elastic soft string. Fast hitters may want more control, spin is not specialized, and frequent breakers can fray it quickly.
For all-court players who value touch and easy depth, X-One Biphase remains one of the strongest synthetic options. The 16 / 1.30mm gauge is the best general starting point, while 17 / 1.24mm adds liveliness for dense patterns.
Frequently Asked Questions
What is X-One Biphase made from?
It uses 50 percent Elastyl fibers, 50 percent H2C fibers, PU 400 polyurethane and a smooth final finish.
What does Biphase mean?
It is Tecnifibre’s pre-stretch process intended to improve tension retention and useful life.
Is X-One Biphase natural gut?
No. It is a synthetic multifilament designed to offer some comparable power, comfort and touch.
Is X-One Biphase powerful?
Yes. Power is one of its defining strengths.
Which gauge should most players choose?
The 16 / 1.30mm version provides the best general balance. Thinner gauges increase response, while 15L increases resistance.
Does X-One Biphase fray?
Yes. Significant fraying is an expected wear indicator for this multifilament.
Can it be used with polyester?
Yes. It can soften a polyester hybrid, but the polyester can accelerate notching and breakage.