All of the Chuckit! balls are specifically designed for the most demanding use by a growing population of fetch enthusiasts. Each ball is compatible with the Chuckit! launchers, so that you do not have to bend down and pick up a slobbery ball. Rebounce Ball - Made with recycled natural rubber, you can feel good about helping the environment while playing with your pooch. Durable Fetch Toy Carefully choose the ball size to fit your launcher. Medium is the standard most common size. All balls fit Chuckit launchers Each ball stimulates a unique aspect of the chase!USA