Exotic Nutrition Silent Runner 9" + Sandy Track + Cage Attachment - Juego de rueda de ejercicio para mascotasSAFE The axle free design eliminates a dangerous center bar, reducing the risk of fur tail entanglement, pet wrap a round, curvature of the spine, and other injuries. SILENT Innovative dual ball bearings create a whisper silent spin. Two stainless steel ball bearings are within the back plate of the wheel, ensuring the wheel glides smooth and silent. The bearings SPIN around the bolt as your pet runs, unlike annoying squeaky wheels on the market that