Say goodbye to cold feet this season and for many seasons after, thanks to ThermaCELL Heated Insoles ProFlex Heavy Duty with Bluetooth. With the innovation of Bluetooth technology, these insoles keep your feet warm in the coldest of elements, up to 5 hours per battery charge. You control the temperature of these super comfortable foam insoles up to 111 degrees F or down to no charge at all, just comfortable insoles. Best of all, you can control it all by an app on your phone! A rechargeable lithium ion battery is embedded in the sole, and the battery can be recharged again and again with the included charger. These'll be the last foot warmers you'll need to buy, so order and enjoy warmth all season long.