600-Denier Polyester. It’s not the size of the sports bag, it’s the amount of work put in that matters. If all you’re looking to take with you is a change of shoes, workout clothes, a hand towel and water bottle then look no further than this very effective sports bag. With rugged 600-denier polyester construction this bag will last a lot longer than those plastic shopping bags you have been using and is better for the environment.