Gerbing's Core Heat Heated Sock Liner These comfortable sock liners are constructed with a moisture wicking material that conforms to your foot for maximum comfort. This form fitting material also helps keep the heat pressed tightly to your foot for superior heat transfer. With Microwire heat technology your feet will stay warm for hours on each charge. If you have ever suffered from cold feet this is the product for you! You can now have warm feet wherever you go. Keep in mind the socks will put out serious heat and you will need to use the controller on the battery to regulate for optimal thermal comfort. Features Wide elastic band Constructed with 4-way stretch fabric Includes two (2) 7V rechargeable lithium batteries that hide away in a calf strap Wiring harness available for use with waders or knee boots This product is not designed to be used on motorcycles Sock heating elements at bottom of foot only 1 year warranty Specifications Core Heat Transfer System 7V 2.2Ah lithium-ion battery Power Source Current 1.4A Watts 7.7W Surface Temp 135F Approximate Heat Output and Duration 100 135F 2 hours 75 115F 3 hours 50 105F 5 hours 25 85F 10 hours Includes rechargeable lithium batteries with a built-in microprocessor controller.