Extra durable, tough and resilient butyl rubber replacement bladders are specifically manufactured for every speed bag we offer. Built for super speed, precision rebounds and professional training. Always keep a spare around for emergencies! XS fits sizes: 4” x 6”, 4” x 7” speed bags, S fits sizes: 5” x 7”, 5" x 8" speed bags, M fits sizes: 6" x 9", 7" x 10" speed bags, and L fits sizes: 8" x 11", 10" x 12" speed bags. Color may vary.