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Head to head

Gosen Polylon PolyBreak 17 (1.24) vs Kirschbaum Pro Line I 18L (1.15)

They split the measurements 3–3. The widest gap is ball bite, where Polylon PolyBreak 17 (1.24) is 37 percentile points ahead. Every figure is a testing-machine result at a fixed reference tension.

Measured, side by side

Gosen

Polylon PolyBreak 17 (1.24)

Polyester · 17 ga

Kirschbaum

Pro Line I 18L (1.15)

Polyester · 18L ga

Stiffness lower = softer, kinder on the arm
19663rd pct
18956th pct
Tension loss lower = stays where you strung it
4987th pct
5089th pct
Energy return higher = livelier, more free power
8519th pct
8516th pct
Spin potential higher = more spin off the string bed
4.235th pct
4.440th pct
Ball bite higher = grabs the ball harder
0.43648th pct
0.37711th pct
String friction lower = strings slide and snap back
0.10468th pct
0.08637th pct

Bars are percentile against all 791 strings, and the marked side is the one that measures better, which is not always the one you want. A firmer bed is worse for your elbow and better for your control, and no measurement knows which of those you came for.

Which one wins, by problem

Each string's standing on the site's rankings, out of every measured string in the database. This is where a comparison stops being arithmetic and starts being a decision.

Swapping between them: what tension?

Bed stiffness is published at one reference tension, so the only honest conversion is to scale it. These are starting points from 52 lb, not prescriptions. The calculator takes your own tension.

Coming from Polylon PolyBreak 17 (1.24) at 52 lb

String Pro Line I 18L (1.15) at 52.1 lb 23.6 kg

Coming from Pro Line I 18L (1.15) at 52 lb

String Polylon PolyBreak 17 (1.24) at 51.9 lb 23.5 kg

Hybrid: what if you used both?

Estimated, not measured. No hybrid combination has been tested as a bed. These figures are the two strings' own lab measurements weighted by how much of the bed each one actually is. Treat them as a guide to which way a pairing moves, never as lab data.

Polylon PolyBreak 17 (1.24) mains / Pro Line I 18L (1.15) crosses

Stiffness60th pct · 1 measured
Tension loss87th pct · 1 measured
Energy return18th pct · 1 measured
Spin potential36th pct · 1 measured
Ball bite42nd pct · 1 measured
String friction62nd pct · 1 measured

Pro Line I 18L (1.15) mains / Polylon PolyBreak 17 (1.24) crosses

Stiffness59th pct · 1 measured
Tension loss88th pct · 1 measured
Energy return18th pct · 1 measured
Spin potential38th pct · 1 measured
Ball bite15th pct · 1 measured
String friction48th pct · 1 measured

Open this in the hybrid builder

Which goes dead first?

Estimated from tension loss, which is the only thing the database measures about ageing. This is when the bed stops playing the way you strung it, not when the string breaks.

Polylon PolyBreak 17 (1.24)

~14 hours of play

Pro Line I 18L (1.15)

~13 hours of play

Both strings in full

Every published measurement
StringGaugePriceStiff lb/inLoss %Power %SpinBite COFFriction COF
Gosen Polylon PolyBreak 17 (1.24) Polyester17find19649854.20.4360.104
Kirschbaum Pro Line I 18L (1.15) Polyester18Lfind18950854.40.3770.086

Add a third string Polylon PolyBreak 17 (1.24) in full Pro Line I 18L (1.15) in full