Difference Between Poly and Co-Poly Tennis Strings

What is the difference between poly and co-poly tennis strings? Are they both made of polyester? How will each of them affect your game, and which one is right for you?

In this article, we’re going to help you find out.

Poly (or Polyester) Tennis Strings

A “poly” string generally refers to a monofilament made from a single polymer called polyethylene terephthalate (PET). A co-poly string is made from polyester and a host of other additives. In this way, co-poly strings have emerged as a reaction to poly strings: They’re designed to avoid some of the problems offered by pure polyester strings.

Let’s dive into why polyester strings became popular in the first place (since they are the base material for both poly and co-poly strings). Then, let’s take a look at the advantages and disadvantages they offer to the average tennis player. Then we can look at how co-poly strings are trying to solve the problems of poly strings.

The History of Poly Strings: How a Simple Material Changed the Game of Tennis

The 1997 French Open final featured a showdown between the two-time champion, Sergi Bruguera, and a relatively unknown 20-year-old from Brazil, Gustavo Kuerten. He was previously ranked #66, and he hadn’t been playing well away from home.

“I’d spent two months in Europe,” he said, “but I didn’t feel good on the court. I’d play one great game and the next I couldn’t put a ball on the court.”

He had to travel back to Brazil to recharge his batteries, and that seemed to be the right decision. When he came back for the French Open, he faced Slava Dosedel, a fierce opponent he had just lost to. This time, though, things were different: He won the first set 6-0; the crowd started to realize that he was a serious competitor.

After just a few more wins, though, he became a household name in France. He took down Thomas Muster, Andrei Medvedev, and Yevgeny Kafelnikov—two of them French Open champions, before taking down Sergi Bruguera in three straight sets.

But, according to Tennis.com, Gustavo “Guga” Kuerten had a secret weapon: “in 1997, Guga was wielding a secret weapon inside his Head racquet: Luxilon Original string. This powerful polyester allowed him to swing for pace, and at the same time, create the topspin needed to keep the ball in the court.”

After the 1997 French Open, Guga jumped from #66 in the world to #15, and, through his early adoption of polyester tennis strings, forever changed the way that tennis was played.

Polyester Strings

Polyester strings offer several advantages, including topspin, control, and durability, but they also come with their fair share of disadvantages, as well.


Polyester strings quickly snap back into place, allowing for maximum topspin (as long as your racquet head speed is quick enough to optimize it, of course). If you’re a recreational player, then, you might not (yet) see much of a difference in topspin just by switching to polyester strings. You haven’t perfected your technique enough to reap the benefits. It’s a little like an overweight cyclist wearing skin-tight spandex: you’re just not fast enough for the little details to matter.

However, everyone improves in time, and success usually comes down to those tiny details so that you can have a slight edge over your opponent.

Topspin isn’t the only advantage of using polyester strings.


There’s an old saying in tennis, “strings loose for power, strings tight for control.”

Polyester strings are very tight, decreasing the dwell time on the racquet. Think about throwing a ball against a wall (a tight string bed) versus a trampoline or pitch back (a loose string bed). When you throw the ball against the wall, you can more easily predict where it will end up. When you throw the ball against a trampoline, though, the results are much harder to determine. The ball could end up almost anywhere, depending on the spin.

A tighter bed string increases control, and polyester is typically very close.

Now, what about the durability of polyester strings?


Polyester strings are some of the most durable strings on the market.

When polyester strings were first becoming popular, one of the biggest drivers for their adoption was their durability. Polyester monofilament strings are some of the best, presumably because they consist of only one material.

(It should be noted; however, that durability and string tension aren’t the same things: durability refers to how long a string lasts while string, tension refers to, well, a string’s ability to keep its tension).

Polyester strings, like all strings, will eventually break — but they’ll last much longer than almost anything else.

What are the Disadvantages of Poly Strings?


The biggest disadvantage of poly strings is that, since they’re strung so tightly, they lose their tension relatively quickly. That means that your string is going to go flat faster and you’ll have to replace it more frequently.

Also, if you’re looking for power, poly strings are probably not your best choice. It all depends on personal preference and playing style, however, so feel free to switch it up. If you’re more of a power player, though, keep in mind that poly strings might not be your best bet.

The old adage stays true: “strings loose for power, strings tight for control.”

Tennis Elbow

Tennis elbow affects anywhere from 10-50% of tennis players throughout their careers. If you’re a serious tennis player, then the chances are that you’ll eventually encounter an arm injury, whether acute or chronic.

Remember: polyester strings are tight. And, if Isaac Newton is to be believed, every action has an equal and opposite reaction, meaning, in this case, that if the strings aren’t absorbing the majority of the shock of each hit (since, again, poly strings are so tight), then your arm is.

If you suffer from tennis elbow, poly strings might make it even worse.

The disadvantages of poly strings aren’t easily sidestepped; that’s why co-poly strings are entering the market.

What are Co-Poly Strings?

As we mentioned earlier, “poly” string generally refers to a monofilament made from a single polymer called polyethylene terephthalate (PET) while a co-poly string is made from polyester and a host of other additives.

The confusion comes from the fact that, long ago, synthetic gut string manufacturers started to use the term “co-poly” to refer to the added polymers in string, not polyester itself. So, when manufacturers advertised a “co-poly” base in their strings, it wasn’t clear whether or not the string was actually tighter and more durable (like polyester) or simply made up of a blend of different polymers (which could give you virtually any result, depending on the mix).

In this case, we’re defining co-poly strings as poly strings with a mix of other additives.

But what do the other additives do? Mainly they attempt to combat the disadvantages of poly strings. Since poly strings lose their tension so easily, manufacturers are experimenting with different types of co-poly strings in order for poly strings to maintain their maintenance for a longer period.

The Biggest Difference Between Poly and Co-Poly Strings

The most significant difference between poly and co-poly strings, then, is that co-poly strings maintain their tightness for a long time while trying to combat the stiffness that causes tennis elbow.

Co-poly strings exist because people are always looking for a stiff, controlled racquet that injures the arm less frequently while providing the same levels of control and power.

Putting It All Together: How Does This Affect Your Game?

So, how do you know whether or not you should choose poly or co-poly strings?

Well, if you’re a less experienced tennis player, it’s safe to say that you can’t generate the racquet head speed to reap the benefits of poly strings. The thing is, though, that since poly strings do less to combat the potential arm feedback, your arm is still going to take the brunt of the impact every time you receive a hard hit. In short: if your technique isn’t yet good enough to generate enough speed, you get all of the disadvantages and none of the advantages.

Co-poly strings, on the other hand, are designed to lessen the impact on your arm. They’ll also need to be restrung less frequently. For these reasons, if you’re a less experienced tennis player, it might benefit you to go with a co-poly string rather than a strictly poly string. Co-poly strings, after all, might be designed for virtually everyone.


A “poly” string refers to a monofilament made from a single polymer called polyethylene terephthalate (PET) while a co-poly string is made from polyester and a host of other additives.

Poly strings first took off in the tennis world when Gustavo “Guga” Kuerten won the French Open with a poly string racquet, taking him from #66 in the world to #15.

Poly strings offer a host of advantages, including increased topspin, control, and durability. They changed the way tennis was played by giving players an increased repertoire of angles and shots.

The problem, though, is that poly strings need to be restrung frequently. If you have any arm injuries (like tennis elbow), poly strings will only make it worse.

Co-poly strings emerged as a reaction to that problem: they try to offer all the benefits of poly strings with none of the negatives.

If you’re an experienced player with great technique, poly strings might be the best choice for you. If you’re a power-player, though, you should look somewhere else.

If you’re a less experienced player, co-poly strings might be a good fit.

Regardless of what you choose, poly strings changed the game of tennis forever, and either poly or co-poly strings might change the way you play tennis, too.