NOVA Walkers Skis are a must for any folding walker. They attach easily on the rear legs to allow the walker to smoothly glide over surfaces, door jams and other terrains. The durable plastic skis last much longer than tennis balls and other glide options. Unlike tennis balls, they also do not track or collect dirt and germs from the ground. The attached rubber tip simply attaches to the tube of the walker leg - no tools required. Fits 1 1/8 inch diameter walker leg.