The Klein Tools 29025 Lithium-Ion Battery powers the Klein Tools Cooling Fan (60155) which is designed for use with Klein Tools hard hats and safety helmets. The battery attaches to Klein's front/back accessory mounts for easy attachment and removal. It powers the dual-fan which forces outside air into the shell to push out stale hot air, facilitating cooling in 16 different configurations for efficient airflow. This modular battery can also charge other small USB devices like headlamps, phones, jobsite speakers, and more.