This 2 Pack features two Bosch CORE18V® 4 Ah Advanced Power Batteries, each of which is a compact battery delivering power in a lightweight solution. It allows you to get the power and lose the weight. The GBA18V40 delivers high power in a compact size for standard to medium-duty applications, such as drilling into concrete, metal and wood; metal grinding; cutting and even light-duty chipping. It delivers 2x the runtime and 60% more power compared to BAT612 18V 2 Ah battery. The GBA18V40 is designed with high-power Lithium-ion cells, featuring a single layer of enhanced 21700 cells for greater battery efficiency. Cutting-edge battery design – includes copper end plates, power rails and a flexible circuit board for reduced resistance and increased efficiency. This Advanced Power Battery has the Bosch-exclusive CoolPack™ 2.0 technology, which cools the battery faster and helps provide longer lifetime compared to Bosch 18V batteries without CoolPack™ 2.0. This compact battery weighs only 1.10 Lbs. but provides performance comparable to much heavier batteries in a lightweight solution. It is compatible with Bosch 18V tools and chargers and the AMPShare™ System. It also has a high-resolution charge-status indicator.