Kaytee Run-About Balls provide the perfect outlet for your under-sized pets oversized energy. These durable exercise and play balls let small animals roam free without getting hurt or lost while creating interactive fun for pets and owners alike. The Mega Run-about ball also fits perfectly onto Kaytee Hamtrac for the safest and most controlled exercise environment. For pet rats and chinchillas 13 Diameter Provides interactive fun for the pet and the pet owner Makes a great temporary holding area to keep your furry friend while you clean their home Encourage healthy exercise in a secure and safe way Note: Always supervise your pets while outside of their cage.