String Project Sirius, monofilament tennis string
String Project Sirius is a competition monofilament tennis string, developed with next-generation materials and additives and designed to deliver high-level performance. Its main strength is control (9.5/10): stable on impact and consistent over time, with 9/10 tension maintenance and 8/10 Arm Friendly® comfort.
- Arm Friendly® Monofilament
- Gauges 1.25 · 1.30 mm
- Next-generation materials
- Tension 17–23 kg
Playing profile
String Project Sirius is a competition string with high performance across the board. Its main strength is control (9.5/10), with a stable response that sends the ball where you aim it. Tension maintenance (9/10) keeps this precision over time, and Arm Friendly® comfort (8/10) makes it playable even in long sessions. Spin (9.5/10) and power (9/10) complete a high-level profile.
- Control9.5/10
- Spin9.5/10
- Power9/10
- Tension9/10
- Comfort8/10
- Resilience8/10
Ratings and technical specifications measured in the laboratory by Pro-t-one (Eng. G. Medri) — laboratory test report 1.25 mm (PDF).
Top performance, on court
On court, Sirius stands out for its control (9.5/10): the response is stable and the ball goes where you aim it, even on the heaviest shots. Spin (9.5/10) and power (9/10) back up every shot, but it is precision that makes the difference. Arm Friendly® comfort makes it playable for a long time.
Precise and stable
Sirius offers top-of-the-range control (9.5/10). Its stable response lets you direct every shot with precision; spin (9.5/10) adds effective rotation.
- Control 9.5/10
- Stable response on impact
- Precise directionality
- Spin 9.5/10
Consistent over time
With 9/10 tension maintenance, Sirius keeps its performance over time. Arm Friendly® comfort (8/10) and natural power (9/10) complete the profile.
- Tension maintenance 9/10
- Consistent performance over time
- Arm Friendly® comfort 8/10
- Natural 9/10 power
Optimised performance
String Project Sirius is developed with next-generation materials and additives, which give it more control and more stability without giving up Arm Friendly® comfort. The result is a competition string with high performance that stays consistent over time.
The manufacturing processes
Spring Load
It allows the molecular chains to contract repeatedly, with minimal tension loss and greater stability of properties over time.
Pre-Stretch
The pre-stretch of the core minimises tension loss and allows stringing at lower tensions.
Double Heating
The heat treatments remove internal stresses and any irregularities in the string, making it more uniform, flexible and elastic.
Liquid Wax
The string is finished with a layer of wax, which reduces wear, significantly extends its lifespan and makes stringing easier.
Low Friction
Reducing friction offers three advantages: less string movement, greater spin potential thanks to better snap-back, and a longer lifespan.
Technical data sheet
| Feature | Value |
|---|---|
| Type | Arm Friendly® Monofilament (next-generation materials) |
| Cross-section | Round |
| Gauges | 1.25 mm (16L) · 1.30 mm (16) |
| Dynamic stiffness | 225 g/mm |
| Static stiffness | 1.05 kg/mm |
| Manufacturing processes | Spring Load, Pre-Stretch, Double Heating, Liquid Wax, Low Friction |
| Recommended tension | 17–23 kg |
The right string if you see yourself here
Competitors seeking control
Those who want to place the ball with precision and look for a stable response, even on the heaviest shots, with high performance in everything else.
Demanding amateurs
Those seeking high-level performance and more control, with the comfort of an Arm Friendly® string.
Those who want consistent performance
Those who need the string to keep its characteristics over time: with 9/10 tension maintenance, Sirius guarantees reliability session after session.