The rechargeable Battery-Operated Shoulder Therapy provides cordless heat, so you can wear it over your clothes and go anywhere. Unlike ordinary heating pads that warm only the surface, the Battery Operated Shoulder Therapy uses Far Infrared Rays (FIR) to penetrate deep into bone and muscle tissue with soothing warmth. The Battery-Operated Shoulder Therapy helps ease shoulder pain from strained, torn or inflamed rotator cuff, separated shoulder, tendonitis and other conditions. Fits left and right shoulder. Available in S/M (chest size 32"-40") and L/XL (chest size 40"-52").