What you should know about POLY:

Polyester strings are popular because the Pros are using them.

The Pros like POLY because they have “snapback” (if hit hard enough), that gives the Pro player more power and more top spin (control).

The Pros restring their rackets before every match and some change to a freshly strung racket every nine games because POLY goes dead so fast.

POLY is a very stiff string which means more stress on the arm (think tennis elbow).

Most club players cannot hit the ball hard enough to create “snapback”, most club players do not restring their rackets before every match, and most club players arms are not as strong as the Pro players arms.

My advice? Do not use POLY unless you are a serious string breaker! Then use a hybrid:  POLY in the mains, a softer string in the crosses, lower the tension, and restring frequently. Do not wait for your strings to break.