Our mega run-about ball measures 13-inch in diameter and is the biggest ball available anywhere. Now provide larger pets with the freedom to exercise. Bigger pets can now enjoy the world around them inside these colorful, oversized exercise balls. Its an excellent source of exercise for pet rats and chinchillas, plus its a fun roly-poly toy for ferrets and a neat pet carrier for guinea pigs. The mega run-about ball also fits perfectly onto super pet's hamtrac raceway for the safest and most controlled exercise environment.