Backaid Heat Therapy patches provide up to 16 hours of targeted, powerful relief from back and muscle pain. Each patch heats up quickly to provide deep muscle relaxation to relieve pain and reduce stiffness. Attach over the area of pain for up to 8 hours. After removal, the patch provides an additional 8 hours of therapeutic pain relief. Backaid Heat Therapy patches are ultra thin so they won't interfere with your day-to-day movement, and can be worn discreetly under clothing. Backaid Heat Therapy patches come in two sizes - wide for lower back and hips, and medium for upper back, shoulders and neck.