M18, 5.0Ah Red Lithium Battery Pack, Red Link Intelligence Provides Optimized Performance & Overload Protection Using Total System Communication Between Tool, Battery & Charger, Best In Class Construction Offers Long Lasting Performance & Durability, Fuel Gauge Onboard Displays Remaining Runtime For Less Downtime On The Job, All Weather Performance Delivers Fade Free Power In Extreme Jobsite Conditions, Powers More Than 60 M18 Cordless Power Tools, Red Link Intelligence Individual Cell Monitoring Ensures Optimal Charge & Discharge For Maximum Life.