Polyester or multifilament: what each does to the ball and to the arm
It is the most asked question about strings, and it is almost always badly framed. Polyester and multifilament are not two levels of quality, nor two levels of player. They are two different structures, which do two different things to the ball, to the arm, and to the life of the string.
Choosing means deciding which of the two matches what you already produce.
Two structures, not two qualities
Multifilament is an assembly: thousands of fine fibres, twisted together and sheathed. It works like a cable. It stretches a great deal under load, and returns a great deal of what it stored.
Polyester is a monofilament: a single extruded strand, sometimes profiled into a square, pentagonal or hexagonal section. It stretches little, it holds its shape, and its edges bite the ball.
Everything that follows comes from those two sentences. There is no hidden third ingredient.
What each one does to the ball
Multifilament returns energy. Contact lasts longer, the ball is carried further, and it leaves faster for the same racquet speed. The trajectory is naturally higher and longer.
Polyester controls through spin. Under impact the mains slide sideways across the crosses, then return to place before the ball leaves the bed. That return — snapback — adds rotation. Polyester does it better than multifilament, not because it is stiffer, but because the friction between its strings is lower: a multifilament, with its sheath and its fibres, grips its own crosses and returns badly.
A counter-intuitive consequence: for the same stroke, polyester gives less ball speed and more rotation. It is that rotation which brings the ball down in the court, and it is what players call "control".
What each one does to the arm
A stiff monofilament transmits noticeably more than a multifilament, on the same frame at the same tension. That is not in dispute, and it is why string is the first lever to look at when the arm pulls, before the racquet.
One factor makes it much worse, and it is more common than the choice of material: a polyester played too long. A dead poly is harder than a fresh one strung three kilos tighter.
Two ways of dying
This is the point nobody makes, and it is the more useful of the two.
Multifilament breaks before it dies. It wears by abrasion: the fibres cut one after another until it fails. As long as it is whole, it plays roughly as it did on day one. When it breaks, it was still playing properly the day before.
Polyester dies before it breaks. It loses tension in the first hours, its edges round off, its notches deepen, and snapback stops. It can stay intact for months — and have been unusable for weeks.
Hence an uncomfortable conclusion: the player who never breaks and plays polyester is often playing the worst string at the club. He gets no signal, so he changes nothing. Knowing when to restring concerns him more than it concerns the breaker.
Who should play what
You break in under three sessions. Polyester is made for you, and a multifilament will cost you more than it brings.
You never break and your arm pulls late in a match. Multifilament, and a low tension. This is the most common case, and the worst served.
You never break and everything is fine. Both work. Take the multifilament if you want more depth, the polyester if you have too much.
You are starting out, or still building your stroke. Multifilament. A full polyester bed only makes sense if you produce the shear that goes with it, and that shear comes from racquet-head speed, not from intent.
Hybrids, and on what conditions
A hybrid puts a polyester in the mains — where the wear happens — and a multifilament in the crosses, where almost nothing happens.
It works on two conditions. The first is that you actually break mains. The second is accepting that the whole bed behaves closer to the stiffer of the two than to the average. A poorly motivated hybrid complicates the reading: you will no longer know which of the two strings produced what you feel.
Natural gut, in one honest sentence
We do not sell it. It remains the reference for energy return and tension maintenance, it is the most comfortable of the three families, it dislikes humidity and it costs several times the price of a synthetic. Saying so is better than pretending it does not exist.
Placing yourself among the seven numbers
Our range covers that whole scale: from N°1, a multifilament, the softest and most generous in return, to N°7, a stiff hexagonal monofilament, the most controlling. N°4 is the most versatile of the seven, and it is the default starting point.
The seven are comparable with each other because they were measured on the same bench, with the same protocol — eighteen elongation curves, not eighteen adjectives. A string name tells you nothing. A number places it.
Settling it in one season
One rule, and it is worth every comparison chart: do not change the material and the tension at the same time.
Start at N°4, play it for three weeks, and move one number in the direction your observations point to. You will have your answer in two restrings, for the price of two restrings — and it will be yours, not a forum's.
The full method, symptom by symptom, is in how to choose a tennis string.
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