The Milwaukee M12 B4 REDLITHIUM-ION 12V 4.0Ah battery offers enhanced performance with up to 2x more run time, 20% more power, and twice the battery life compared to previous technologies. It features individual cell monitoring for optimal charge and discharge, ensuring maximum lifespan. The integrated weld frame and rubber overmold provide durability against vibrations, bumps, and drops. Its temperature management system keeps the battery in an ideal temperature range for sustained performance. This battery is compatible with all Milwaukee M12 cordless power tools.