Use this HOTRONIC XLP 1P BT Battery Pack with any Hotronic Heated socks to keep them heated up for all-day warmth. The XLP 1P BT battery pack offers constant heat and is simple to control via an app on our smartphone which allows us to control the lithium-ion batteries while avoiding bending over in ski boots. A new compact battery design makes this set more lightweight and more powerful, so grab some socks, download the app, and get ready to thrive in the cold.