Up to 24 hours of continuous warmth for your feet, controlled from your pocket. The Hotronic XLP 2C BT Custom FootWarmer Set features dual Lithium-Ion battery packs with three constant heat settings plus a Power Boost mode, all adjustable via the button on the battery pack or remotely through the free Hotronic Heat app on your Bluetooth-enabled smartphone. The app provides a real-time overview of charge status and heating levels, so you can fine-tune your warmth without exposing the batteries to the cold or removing your boots. The kit includes heating elements with Cambrelle covers designed for easy integration with any insole, whether preshaped or custom. Rechargeable via the included USB charging cable, compatible with wall adapters, power banks, or vehicle chargers worldwide. Compatible only with Hotronic XLP systems — not compatible with S4 or older systems.