Run-about Balls have been a favorite pastime for years, providing pets and pet owners with interactive fun during playtime. Sized perfectly for hamsters and gerbils, the Clear Run-about Ball provides the perfect outlet for your pet's excess energy. Run-about balls also make a great temporary area to keep your furry friend while you are cleaning their cage. For added safety, use your Run-about Ball on Super Pet's Hamtrac Raceway and provide your pet with a controlled exercise environment.7 Diameter - UPC: 45125613506