The Therm-ic PowerSock S-Pack 1400 Bluetooth is compatible with your Therm-ic heated socks for lasting warmth that will keep your toes toasty during the chilliest days on the mountain. The battery pack sits high enough that it won't conflict with your ski or snowboard boot, and it's rechargeable via USB for up to 16 hours of warmth. For seamless control of the heat level, this battery pack connects to your smartphone via Bluetooth, meaning you don't have to fumble with your sock every time you need to change the setting.