The Thermacell Heated Insoles offer convenient remote operation, no wires or external batteries, and at least 2,500 hours of toasty heat to warm cold feet for about four winters of heavy use. They operate by a wireless remote control while the foot warmer is inside your shoes or boots. They use high-tech wireless thermal technology, no wires, extension cords, VELCRO straps, or battery strap brackets. And they have no batteries mounted to the ankle, shoe, or waist. Charge lasts up to five hours of constant use. Finally, powered by rechargeable, built-in lithium-ion polymer batteries embedded in the foot warmer insoles.