Alfie Pet by Petoga Couture - Joseph Exercise Running Ball for Mouse, Chinchilla, Rat, Gerbil and Dwarf Hamster Measures 5.25" both in length and width. 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. Also make a great temporary area to keep your little critter while you are cleaning their cage. Made from shatter-resistant plastic, great ventilation, and screwed together segments for durability.