The ActionHeat 3.7V battery heated socks are the perfect blend of quality and comfort. The Rechargeable ActionHeat socks reach a maximum temperature of 140F and can last up to 8 hours. ActionHeat battery heated apparel utilizes innovative technology designed to warm the core body temperature. These revolutionary garments feature built-in heating panels and are made with ActionFlex material that provides lightweight warmth, comfort, and versatility.ActionHeat heated garments use FAR infrared heating and ActionWave heat reflective technology to deliver hours of heat and comfort. ActionHeat allows you to stay warmer and enjoy outdoor winter activities longer than ever before. HOW TO USE: Power Up – Charge the provided ActionHeat 3.7V batteries. Plug-In – Connect the batteries to the cords located in the pocket on the top of the sock. Turn On – Press and hold the power button on the battery for 3 seconds. Features: Built-In heating panels strategically placed on the top of the toes use advanced ultra-fine fibers to provide superior heating performance Battery Voltage: 3.7 Volt Colors Available: Black Machine Washable using provided mesh wash bag only (gentle cycle)  Heats 8+ Hours Unisex Fit Sizes Available: S/M, L/XL, XXL Estimated Heating Times: High (Red): 140F – 4+ Hours Medium (Orange): 120F - 6+ Hours Low (Green): 100F – 8+ Hours Material Contents: Material Content: 44% Acrylic, 18% Polyester, 16% Wool, 14% Nylon, 7% Cotton & 1% Spandex Ultra-fine carbon fiber heating panels. Includes: (2) ActionHeat Wool Blend Socks w/ Heated Toes (2) 3.7 Volt 2.2AH Lithium-Polymer Rechargeable Batteries (1) Dual Battery Charger Kit