The ThermiPaq Medium Hot & Cold Pain Relief Wrap uses a thermal ceramic compound made from all-natural, clay-based materials. Developed by a former NASA engineer, this revolutionary "Theramics"€Ã‚ compound utilizes radiant energy to create a deep penetrating, therapeutic system for hot and cold applications. ThermiPaq's radiant energy offers distinct advantages transferring heat and cold slowly and evenly to your affected pain area. This allows Theramics therapy to penetrate deeper and more effectively. The Medium Therapeutic Hot & Cold Pain Relief Wrap conforms to all parts of the body including the back, knees, ankles and elbows. The clay-based properties of Theramics enable you to easily mold the ThermiPaq pad to any affected area for better pain relief. ThermiPaq is safe and easy to use. Our radiant energy technology allows ThermiPaq to heat evenly throughout without generating any hot spots that can harm your skin. For hot therapy, the pad quickly heats in the microwave (see instructions for actual times). For cold therapy, place the pad in the freezer and it is ready for use in one hour. Features: Clay based hot & cold therapy Deep penetrating relief Reusable Soft cover with Velcro® straps