String Project Sirius tennis string is a smooth co-polyester string that blends control, spin, and consistency into a dependable all-round performer. Designed for competitive players, Sirius offers a crisp yet comfortable response and rewards clean ball striking with confidence-inspiring control. It doesn’t chase raw power or plushness — instead, it focuses on stability, predictability, and a refined feel that holds up over long sessions. It’s a string for players who value precision and a connection to the ball over a trampoline-like response.
Quick verdict
String Project Sirius tennis string delivers a balanced mix of control, spin, and feel that’s easy to trust from the baseline. Spin comes naturally without being overly shaped or harsh, and tension stability is strong enough to maintain consistent performance over time. Comfort is respectable for a control poly, and it retains a lively response even after multiple sessions.
What the numbers and lab tests say
Independent lab-style scoring for String Project Sirius below.
String Project Sirius — Indicative Performance Scores
Controlled pop; prioritises precision over free power.
Moderate stretch; crisp but not overly stiff.
Strong bite and reliable snap-back for topspin players.
Predictable, stable trajectories on full swings.
Good tension stability for a performance poly.
Consistent feel for most of the string’s lifespan.
Reasonably arm-friendly for a poly with this level of spin.
Lab testing shows Sirius excels in both spin (95%) and control (95%), confirming its strengths as a stable, precision-oriented poly. With power (80%) and resilience (80%), it maintains a solid level of liveliness without feeling overly stiff or dead.
Tension holding (80%) and stability (85%) results indicate that performance remains consistent over long play sessions — ideal for players who don’t restring every week. On the weaker side, elasticity (55%) and comfort (65%) reflect a firmer response that’s typical of performance-driven polys.
👉 Overall, Sirius ranks as a balanced, spin-friendly poly with excellent predictability and a crisp, responsive feel that holds up over time.
How it plays (feel, spin, power, control)
On court, String Project Sirius tennis string feels clean and connected — firm enough to control heavy hitting, yet not so stiff that it feels harsh. Spin generation is effortless and controlled, helping the ball dip sharply inside the baseline without losing depth.
The feel is crisp and direct, giving clear feedback on contact, especially from the baseline and on volleys. Power sits in the medium range, letting you take big cuts while keeping your shots on target. Compared to softer polys, Sirius gives you more precision and a slightly firmer pop, ideal for players who hit through the court.
It’s less elastic than Yonex Poly Tour Pro but more stable and predictable. Compared to Head Hawk Touch, it’s firmer and offers greater shape retention, while Grapplesnake Tour Sniper feels a touch springier but less consistent in tension.
String Project Sirius – Pros & Cons
String Project Sirius – Here’s a quick pros and cons snapshot:
Durability & tension maintenance
Tension holding (80%) confirms that Sirius maintains performance across multiple hitting sessions with minimal drop-off. The stringbed stays consistent, giving you a dependable response for longer than many mid-firm polys.
Durability is solid for a 1.25mm gauge, resisting notching well thanks to its slick surface that helps preserve snapback. Players who hit big topspin won’t see a sudden loss in control — just a gradual, predictable decline over time.
👉 Overall: Sirius is a durable, stable poly that holds tension well and performs reliably throughout extended play — perfect for frequent players seeking consistent response without constant restringing. See my guide here on choosing the right tennis string tension.
Who it suits
Best For:
- Intermediate to advanced baseliners who value spin and directional control
- Players who want consistent response and reliable tension
- Those who prefer a firmer, connected feel without excessive stiffness
Not For:
- Beginners or players needing free power
- Anyone with arm sensitivity seeking maximum comfort
- Players who prefer softer, more elastic polys
Best suited racquets
String Project Sirius tennis string pairs best with control-oriented or spin-focused racquets that benefit from its crisp and stable response:
| Racquet Type / Feature | Why Sirius Works | Notes |
|---|---|---|
| Spin / Open-Pattern Frames (Pure Aero, Extreme MP, VCORE 100) | Amplifies spin and bite while keeping the launch angle predictable | May require 1–2 lbs tighter tension for added control |
| Control / Precision Frames (Blade 98, Prestige Tour, Percept 97) | Adds liveliness and spin while maintaining clean directional feedback | Firm response — hybrids or slightly lower tension improve comfort |
| All-Court / Power Frames (Ezone 100, TF40 305) | Refines depth control and accuracy in racquets with more pop | Great balance of feel and stability |
Comparable strings
Players considering Sirius might also like:
- Yonex Poly Tour Pro – softer and smoother, but less control and spin bite.
- Head Hawk Touch – slightly softer feel with more dwell time but less direct feedback.
- Grapplesnake Tour Sniper – more springy and powerful, but less consistent tension retention.
👉 In summary, String Project Sirius tennis string sits comfortably among the best modern control polys — stable, spin-friendly, and impressively consistent across long sessions.or advanced players who want a firm, high-performance string that keeps its edge over time.
Practible recommendations
Tension: Start at 50–52 lbs for a balanced setup. Drop by 2 lbs for more comfort or go tighter for added precision.
Gauge: 1.25mm hits the sweet spot between spin and durability. Frequent breakers may consider 1.30mm.
Hybrid Setup: Works well with softer crosses (synthetic gut or multifilament) to enhance comfort and touch.
Restringing: Expect consistent play for around 10–15 hours of hitting. Competitive players may restring sooner.
I hope this review helped you understand what String Project Sirius tennis string is, who it works for, and what to expect from it over time. If you want to know if Sirius (or another string) is right for your game or if you’re ready to book a restring, just send us a message via chat!
