Thumpers Sport patented drive system technology transmits energy deep into the muscle tissue. Variable speed control from 20 to 40 pulses per second that match your muscles natural healing frequency. A True Speed feedback system that prevents low-speed stalls. Interchangeable spheres that let you customize your massage experience. The long ergonomic handle makes it easy to reach all muscle groups, back, and legs and works well as a shoulder massager. Easy to clean, just wipe with a damp cloth