Exotic Nutrition Silent Runner 9" - Exercise Wheel + Cage Attachment Ideal for Hamsters, Gerbils, Mice (12" size available for Sugar Gliders, Hedgehogs, Chinchillas, Rats) Safe, solid running surface with no pinch areas. Textured running tracks for non-slip, excellent grip. Includes Cage Attachment for mounting. Made without a center axle, so no risk of spinal injury or tail / fur entanglement. Natural bean-shaped openings for safety and containment. Pet-preferred solid black walls. Innovative ball-bearings allow the wheel to roll completely smooth and silent. Approx size: 11" tall (on stand) x 3" wide (2.5" wide track) x 9" diameter. PLEASE MEASURE CAGE. FAST, FREE SHIPPING! Avg 3 days! ZooPro sells exotic animal foods and accessories that are manufactured by Exotic Nutrition Pet Supply Company. Exotic Nutrition has been the industry leader of exotic animal products since 1998, specializing in sugar gliders, hedgehogs, prairie dogs, marmosets, degus, skunks, opossums, chinchillas, rats, hamsters, gerbils, squirrels, rabbits, guinea pigs, rodents, ferrets, chickens, bluebirds, wild birds, monkeys, marsupials, reptiles, amphibians, & more