Bosch BAT620 18-Volt Lithium-Ion 4.0Ah Battery with Digital Fuel Gauge Compatible with all Bosch 18-Volt Lithium-Ion tools and chargers Unique Cool Pack Design: Special heat conductive housing and ribbing pulls heat away from inside the battery, keeping the battery cooler Up to 2x Battery Life: Bosch COOL Pack manages battery cells temperature reducing heat-up, which is the main eradicator of every battery cell Integrated Fuel Gauge: LED Indicator for battery stage of charge Durable Housing: Survives 3-Meter drop