Therafin Walker Tennis Ball Glides have a special housing that allows tennis balls to rotate. Indoors and out, nothing beats the stability and the versatility of these glides. Indoors, they quietly glide over linoleum and wood floors without leaving marks. Outdoors, the round shape and tough exterior are the perfect combination for overcoming rough, uneven surfaces. Internal stabilizers provide exceptional stability and quiet operation. The molded internal stabilizer provides exceptional stability attaching the tennis ball onto the walker leg. The stabilizer also protects the tennis ball from sharp edges of the walker leg, extending the life of the tennis glide. Easy installation; compatible with any standard walker with 1" diam. tubing. Tennis balls included. Not made with natural rubber latex.