Heat Factory's air activated Adhesive Body Warmer provides 10 plus hours of therapeutic pain relief from sore muscles, stiffness, arthritis and much more. The heat patch is a soft, odorless lightweight adhesive pouch containing an inert mixture of iron powder, charcoal, salt, water and vermiculite. Apply adhesive side of heat pack to clothing NOT directly to skin. When warmer is exposed to air, a natural exothermic reaction generates consistent and prolonged heat. 40 warmers are included in this purchase.