Polyester strings make up the majority of stringing jobs in most pro shops today—and yet they are the most commonly misused material. Too stiff, strung too tight, in the wrong racquet, for the wrong player—the consequences range from poor performance to real injuries. This guide explains what poly actually is, who it is suitable for, and how to correctly install and recommend it.
How polyester strings are constructed
Polyester is a monofilament string—a single continuous polymer strand extruded to a uniform diameter. The material is inherently stiff, which gives poly its defining characteristics: durability, low power (low resilience), high spin potential, and rapid tension loss.
Stiffness is not uniform across all polyester strings. Manufacturers adjust it through co-polymer formulations, surface coatings, and cross-section shapes. A shaped poly string—pentagonal, hexagonal, twisted—bites into the ball differently than a round one.
Why players choose polyester
Durability. A hard-hitting player who breaks multifilament strings every session can often play for weeks with a poly string. For players who destroy strings faster than the tension drops, poly eliminates the hassle and expense of frequent restringing.
Spin potential. Polyester strings move laterally during ball impact and snap back into their original position. This snapback effect increases the ball's dwell time on the string bed and enhances topspin generation.
Control. The lower power (resilience) of a stiff poly string allows players with fast swings to swing out fully without hitting the ball out of bounds.
When you should not recommend poly
- Beginners and juniors do not possess the swing speed required to sufficiently compress a poly string bed.
- Players with arm problems—lateral epicondylitis, wrist pain, shoulder issues—should avoid full polyester setups.
- Players with slower swings at any level will find polyester disappointing.
For players on the boundary of these categories, a hybrid setup is often a better solution.
Selecting the right gauge and stiffness
Polyester strings are typically available from 1.15 mm to 1.30 mm. For most club players trying poly for the first time, 1.25 mm is the practical starting point.
Choosing the right tension
Polyester should almost always be strung at a lower tension than the player's previous string. A practical starting point is to reduce the player's multifilament tension by 10% to 15%. Adjust this based on their feedback.
Polyester also loses tension faster than other string types—often dropping 10% to 20% in the first 24 hours after stringing.
What to communicate to the customer
- The tension drops noticeably within the first 24 hours—this is completely normal.
- The string does not need to break to signal a replacement—it "dies," typically after 20 to 30 hours of play.
- Regular restringing on a schedule is particularly important with polyester.
Polyester is the right string for a specific type of player. Making this recommendation correctly and communicating it clearly is where a stringer's expertise becomes apparent.