No wires or batteries needed. This water resistant foot warmer offers up to 2 500 hours of comfortable heat to cold feet. It is rechargeable and operated by a wireless remote with 3 settings; High Medium and No Heat. High heats up to 111 degrees Fahrenheit. The rechargeable battery is a lithium-ion polymer battery which is embedded in the foot warmer insole. Dont worry about the cost of charging; it comes out to .05 cents/hour! The charge lasts up to 5 hours on medium heat. The package includes 2 heated insoles with batteries 1 remote control with battery 1 lanyard 1 drawstring travel bag 1 global charger and 1 instruction booklet. Fits men shoe sizes 3.5- 13 and women shoe sizes 4.5-14 and can be trimmed to fit any size in-between.