A must have for those hard to get at spots around the hand , shoulder and knees . The Trigger Wheel features a single rotating nylon wheel especially effective in areas too small or difficult to target with other massage tools. It is especially effective at myotendon and bony junctions. Use the Trigger Wheel to replace the thumb around small, difficult areas like the jaw, neck and skull area, trapezius, parascapular, pectorals, elbow, wrist, knee, ankle. A "must have" for those suffering from RSI or overworked muscles from computer use!