Bosch 18 Volt FatPack Lithium-Ion 4.0 Ah Tool Battery (2-Pack)

Maximum run time, 4.0 Ah capacity. Unique CoolPack design offers an advanced heat conductive housing that keeps the battery cooler. Integrated fuel gauge for fast and easy charge status. Durable housing will survive 9 ft. drop. Flexible power system (FPS) works with all Bosch 18V lithium-ion tools.