Web Exerciser allows the duplication of virtually all joint actions including flexion, extension, opposition, abduction and pronation and supination. It measures 35.5cm in diameter and weighs 453gms. It's unique patented design allows a variety of exercises to be performed comfortably and effectively. Constructed of high quality rubber with special agents added for durability and strength. The Web Exerciser will last for years (with proper use and care).