Designed to keep your feet warm, not hot, to avoid having your feet to sweat and freeze. Can be cut to fit your shoes size. Rechargeable foot warmer is operated by a wireless remote control with a range of 2,1m (7ft). Adjustable to three temperature settings: no heat, medium and high. Powered by rechargeable, built-in lithium-ion polymer batteries embedded in the foot warmer insoles. Charge lasts up to 5 hours of constant use (on medium heat setting), can be recharged at least 500 times and recharges in 4 hours or less. Bag, charger and remote included. Sizes Chart (US-CAN): Small: 4.5 to 6 Medium: 6.5 to 8 Large: 8.5 to 10 X-Large: 9.5 to 11 XX-Large: 11.5 to 13