FATPET&reg; Kerry Run-About Small Animal Exercise Toy Pet Run Ball for Small Pet Hamster and Mouse Clear ball provides interactive fun for you and your pet. Ideal for hamster, mouse and other small furry animals. Made with pet safe materials. Easy to clean and resistant to odors. Relieves boredom and increases activity level Measure: 12cm/4.7" in diameter and 12cm/4.7" in height. Its entrance hole measures 7cm/3" in diameter.