Milwaukee M18B4 18V 4.0Ah Red Lithium Ion Battery Delivers up to 2.0x more run time, up to 20% more power and up to 2x more battery life compared with other Lithium-Ion technologies and / or with previous Milwaukee battery technology. (Results depend on tool and application). Features: REDLINK Electronic Intelligence Overload protection to prevent battery abuse Temperature Management system to keep battery at ideal temperature Individual Cell Monitoring for optimal charge and discharge for maximum battery life Discharge Protection prevent cell damage from over-discharging For use with MILWAUKEE M18 cordless tools 2x More Run-Time 20% More Power 2x More Recharges Specification: Voltage: 18 V/4.0Ah Battery Type: Lithium-ion REDLINK intellegence: Yes Battery fuel gauge: Yes Weight: 0.72Kg