Recharges in 4 hours, water resistant, powered by built-in lithium-ion polymer batteries embedded in the insoles. Uses high-tech wireless thermal technology—no wires, extension cords, Velcro® straps, or battery strap brackets, and no batteries mounted to the ankle, shoe, or waist. Can be recharged up to 500 times using the included charger. Package includes: 2 Heated Insoles equipped with integrated rechargeable lithium-ion polymer batteries; 1 remote control with battery; 1 lanyard; 1 drawstring travel bag; 1 global charger; 1 instruction booklet. Customizable Sizes for Men and Women, can be trimmed to fit almost any shoe size.