Many small pets require a good physical workout. Lee's® offers the most complete line of small-animal exercise balls to satisfy the needs of most small animals from dwarf hamsters to ferrets and chinchillas. Kritter Krawlers® allow pets the freedom to roam while being safely confined and they quickly learn to maneuver around common household obstacles with ease. Features include: ribs inside to provide better gripping power for pets, shatter-resistant plastic construction, and ventilation openings. The standard 7" Kritter Krawlers® designed for use by hamsters, gerbils, and other small animals. Animal species vary greatly in size. Choose the size that best suits the needs of your pet.