Features: Exercise wheel for small pet such as hamster, gerbil and rat, maximum diameter 21cm. Adopt strong steel shaft and premium grade PP material; With thick wall and round edge. No gaping place, your pet won't get its feet hurt or wrenched. Non-slip convex lines enlarge friction and enhance stability to avoid false step. Silent structure, your animal can run at night without disturbing others. Wide suitability, can be mount on various pet cage. A funny toy help to keep your pet slim and healthy.