Keep your feet warm longer with extra batteries for ThermaCell Heated Insoles ProFlex. With extra batteries charged and ready, you can work or play outdoors all day in comfort. It inncludes 2 rechargeable lithium-ion polymer batteries, 1 USB cable, 1 wall charger, and 1 smart charging case. The batteries fit Thermacell Heated Insoles ProFlex and each charge lasts up to 5 hours. The batteries charge in 4 hours or less. You can use wall charger (included with ThermaCELL Heated Insoles ProFLEX) or any USB port to charge. The wall charger wires disconnect so charger can be a carrying case for batteries.