Polyester strings have been all the rage in tennis the past 4 years. The polyester or co-poly strings that you hear about are used by almost the entire worldâ€™s touring professionals. Luxilon is the most used brand by tennis professionals and there now there are so many string companies making these co-poly strings. First the good news, polyester strings are great for durability and spin. The smooth surface and coating allows the string to snap back into place during contact so that it helps produce more spin on the ball. Now the bad news. Co-poly string lacks power, it lacks comfort and it lacks tension holding properties. Polyester strings are more affected by weather and temperature than any other type of string. They will lose 50% of the tension after just 20 hours of play. Yes, thatâ€™s half your string tension is lost. The touring proâ€™s get their strings for free and have them strung and restrung before every match. Their strings only need to last 2 to 3 hours or less. They will change racquets after 9 games just to match the tension they had at the beginning of the match. So what does this mean to you? Well, polyester might not be the best string for you unless your break your strings every 4 hours of play. Durability is great but it comes at a cost with shock and arm problems caused by co-polys and polyester strings. Itâ€™s much better to use Natural Gut if you can afford it. Next best is the Multifilament nylon strings and then nylon Synthetic Gut. Better to restring often and have the best string performance than keep old, dead, strings in a racquet for years.