18V LXT, Lithium Ion, 4.0Ah, Battery, Extended Run Time, Powers 18V LXT &18V Compact Tools, Integrated LED Battery Charge Level Indicator Allows User To Monitor Battery Charge, Provides Up To 35% More Run Time Per Charge, Reaches Full Charge In 40 Minutes Or Less, Compatible Only With Star Protection Tools, Indicated By The Star Symbol & Or Yellow Battery, Receiver Under The Tool, Delivers Consistent Power & Run Time In Extreme Temperatures Even In Winter - 4 Degrees Fahrenheit 20 Degrees Celsius, Equipped With Star Protection Computer Controls To Protect Against Overloading, Over Discharging & Over Heating, Impact Resistant Outer Case & Shock Absorbing Inner Liner Are Engineered To Protect The Battery, 16 Contact Terminals Maintain A Constant Connection With The Tool To Help Prevent Power Loss Or Fluctuation, Even During High Vibration Application.