Alfie Pet by Petoga Couture - Tommy Running Exercise Wheel for Mouse, Chinchilla, Rat, Gerbil and Dwarf Hamster The wheel is 5" wide while the ball itself is 4.5" diameter Ideal for hamster, mouse and other small furry animals. This is a fun way to exercise your small animal pets; relieves boredom and increases activity level. They will love it and be entertained for hours. Can be free standing or rolling around by removing the stand which allow tiny pets to maneuver with greater ease. Made from shatter-resistant plastic, great ventilation, and screwed together segments for durability.