Spring Load
It allows the molecular chains to contract repeatedly, with minimal tension loss and greater stability of properties over time.
Arm Friendly®
String Project Keen
Thin, sensitive, responsive: feel every shot.
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.
8.5/10
Comfort
9/10
Spin
8/10
Power
Technical Specifications and On-Court Ratings
Thin-Gauge Sensitivity and Responsiveness
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.
Power8/10
Comfort8.5/10
Control7.5/10
Resilience8.5/10
Spin9/10
Tension7/10
Ratings measured in the laboratory by Pro-t-one (Eng. G. Medri), as are the technical specifications.
Designed to Be Thin
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.
Technical Data Sheet
- Cross-section
- Round
- Available gauges
- 1,13 (18) · 1,18 (17) · 1,22 (16L)
- Dynamic stiffness
- 230 g/mm
- String Stiffness Emulator
- 225 lb/in
- Static stiffness
- 0.8 kg/mm
- Tension range
- 18 / 23 Kg
Laboratory test report · Pro-t-one (Eng. G. Medri)
Technology and Design Optimised for the Thin Gauge
String Project Keen is made of co-polyester, with additives specially developed to make it thin and tough. The result is a string that combines the sensitivity of a thin gauge with durability beyond expectations for this thickness.
The manufacturing processes
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.
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
What the Experts Say
Independent reviews published by testers and specialist outlets.
Who It's For
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.
Ready to Discover Extreme Sensitivity?
Choose the format that best suits your needs. Free shipping from €50.
200 m Reel
~17 stringings
-
~€6.41 per stringing
- Free shipping
- 1 Dampener
- 2x Dry Overgrip pack
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Pack of 6 Sets
6 stringings
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~€8.98 per stringing
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- 1 Dampener
- 2x Dry Overgrip pack
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Pack of 3 Sets
3 stringings
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~€9.97 per stringing
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- 1 Dampener
- 2x Dry Overgrip pack
Gauge:
Single Set
1 stringing
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- Free shipping
- 1 Dampener
- 2x Dry Overgrip pack
Gauge:
Frequently Asked Questions (FAQ) about String Project Keen
What is String Project Keen?
String Project Keen is a thin-gauge co-polyester monofilament tennis string (1.13-1.22 mm): sensitive, responsive and tough. It offers spin (9/10), power (8/10) and Arm Friendly® comfort (8.5/10), with resilience (8.5/10) that is high for such a thin gauge.
Why choose a thin gauge?
A thin gauge (1.13-1.22 mm) offers a more direct and sensitive feel and immediate responsiveness. Keen is designed to exploit these advantages: spin comes from snap-back, and comfort and durability are beyond expectations for this thickness.
At what tension should String Project Keen be strung?
The recommended tension range is between 18 and 23 kg. With thin gauges it is advisable not to exceed 22 kg to maintain Arm Friendly® comfort and optimal durability.
Which gauges is String Project Keen available in?
Keen is available in three gauges: 1.13 mm (18G) for maximum sensitivity and spin, 1.18 mm (17G) for the ideal balance, with exceptional ball launch, and 1.22 mm (16L) for more control, durability and tension maintenance.
Is String Project Keen suitable for players with arm problems?
Yes, Keen is Arm Friendly®, with 8.5/10 comfort, one of the highest in the range. Despite its thin gauge, String Project manufacturing technologies and heat treatments ensure excellent vibration absorption.
How long does String Project Keen last compared to standard-gauge strings?
Keen is designed to be thin and tough: it does not break easily and its durability is beyond expectations for strings of this thickness. Resilience is 8.5/10 and tension maintenance 7/10; with the 1.18 and 1.22 mm gauges, tension maintenance improves.