BAT621 18 V Li-Ion 5.0 Ah FatPack Battery:
The new 5.0 Ah 18V Bosch FatPack battery offers 25% more runtime (Compared to Bosch 4.0 Ah) and more than 65% more runtime (Compared to 3.0 Ah). CoolPack Design technology, including advanced heat conductive housing, keeps the battery cooler for 2X longer recharge life. Check the charge status quickly and easily using the integrated fuel gauge. These batteries are designed to work as hard as you, So working in cold weather down to -4°F is no issue. The BAT621 is compatible with all Bosch 18V Lithium-Ion power tools, Radios and more.