Wind & Fire 3600mAh Rechargeable Double Side Hand Warmer w/Titanium Surface Ergonomic design and titanium surface otection and heat insulation, aerospace feather light titanium to achieve light weight and best in class heat conduction Two side fast heating, 20 seconds to 50C. Generate constant heat regardless of battery level Long operating time: last 6 hours in Low temperature (122 F) High (140 F) /Low (122 F) temperature setting. Accurate temperature control and 2 digits thermometer display (Celsius) 3600 mAh Rechargeable high temperature resistance Li-ion battery.