The ThermiPaq Hot & Cold Pain Relief Wrap uses a thermal ceramic compound made from all-natural, clay-based materials to retain heat when heated and stay cool when frozen. Developed by a former NASA engineer, this revolutionary "Theramics," 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.