Review on 🐹 6'' Hamster Exercise Ball: Small Animal Toy for Running, Jogging Wheel, and Activity – Transparent Ball for Mice and Rats by Courtney Wang

There are holes on both ends and they move. They are not securely attached. The dog accidentally kicked one of the balls and it fell apart, didn't even break it just fell apart. So, the house mouse ran, it took 20 minutes to get it out from under the dishwasher. It's only a matter of time before a hamster hits a wall or other object hard enough and falls apart. Don't trust these balls. They are too big for house mice, but they could move. Perfect size for a hamster.