The Kaytee Comfort Wheel for small pets features a safe, solid running surface, quiet operation and a "tail-safe" design, allowing pets an easy entrance and exit. Safe, solid running wheel for small animals Easy entrance and exit for pets Features free standing and cage attachment options Every Comfort Wheel comes with a heavy duty wire stand and a 2-way attachment clip, so the wheel can be used either free-standing or clipped to a wire cage. Great for hamsters, rats, and other small animals. Sizes: Small: 5.5" Diameter Large: 8.5" Diameter Giant: 12" Diameter Note: Wheels ship in assorted colors. Please allow us to choose one for you.