String Project Keen, thin-gauge monofilament tennis string
String Project Keen is a co-polyester monofilament tennis string designed for thin gauges: sensitive and responsive, but also tough. Available in 1.13 mm, 1.18 mm and 1.22 mm gauges, it is designed for those seeking feel, spin and responsiveness. Arm Friendly®, with 8.5/10 comfort.
- Arm Friendly® Monofilament
- Gauges 1.13 · 1.18 · 1.22 mm
- High-sensitivity thin gauge
- Tension 18–23 kg
Playing profile
String Project Keen offers spin (9/10) that comes from its fast, effective snap-back. Comfort (8.5/10) is high for such a thin string, thanks to String Project manufacturing technologies: Keen is Arm Friendly®. Power (8/10) is responsive and immediate, and resilience (8.5/10) comes with breakage resistance beyond expectations for this gauge.
- Spin9/10
- Comfort8.5/10
- Resilience8.5/10
- Power8/10
- Control7.5/10
- Tension7/10
Ratings and technical specifications measured in the laboratory by Pro-t-one (Eng. G. Medri) — laboratory test report 1.18 mm (PDF).
Extreme performance and sensitivity on court
On court, Keen makes itself felt: the feel is direct, sensitive and communicative, and every shot is clearly perceived. Spin comes from a fast snap-back, and responsiveness is immediate, with a quick ball launch. All with a stable response you wouldn't expect from such a thin gauge.
Direct, sensitive feel
Keen's thin gauge offers a direct, sensitive feel: you feel where you hit the ball and can adjust your shot accordingly.
- Direct, communicative feel
- Superior touch sensitivity
- Gauges from 1.13 to 1.22 mm
- Precise impact perception
Spin and immediate responsiveness
With 9/10 spin and 8/10 power, Keen responds instantly. Spin comes from its fast, effective snap-back; drive is quick and resilience (8.5/10) keeps it that way over time.
- Spin 9/10 from snap-back
- Power 8/10, responsive and immediate
- Resilience 8.5/10
- Fast, effective snap-back
Design optimised for the thin gauge
Keen is designed from the outset for a thin gauge. That is why, despite its reduced thickness, it has excellent mechanical strength and does not break easily. The thin gauge brings a direct, sensitive feel that lets you perceive every nuance of impact.
The manufacturing processes
Spring Load
It allows the molecular chains to contract repeatedly, with minimal tension loss and greater stability of properties over time.
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® thin-gauge monofilament |
| Cross-section | Round |
| Gauges | 1.13 mm (18) · 1.18 mm (17) · 1.22 mm (16L) |
| Dynamic stiffness | 230 g/mm |
| Static stiffness | 0.8 kg/mm |
| Manufacturing processes | Spring Load, Double Heating, Liquid Wax, Low Friction |
| Recommended tension | 18–23 kg (with thin gauges it is best not to exceed 22 kg) |
The right string if you see yourself here
Those seeking extreme sensitivity
Players who want to perceive every nuance of impact with the ball and prefer a direct, communicative feel that only a thin gauge can offer.
Spin-oriented players
Those who want spin and responsiveness: Keen's fast snap-back loads the ball with spin and sends it quickly off the strings.
Those seeking comfort in a thin gauge
Those who normally avoid thin gauges for fear of stiffness or poor durability. Keen is Arm Friendly®, with 8.5/10 comfort, and is designed to hold up even with its reduced thickness.