The dual-voltage 20V/60V MAX FLEXVOLT 9.0 Ah battery automatically changes voltage when you change tools, providing up to 6X runtime in 20V MAX tools and the power of corded in 60V MAX and 120V MAX tools. Take on tough jobs with this battery because patented technology and large format cells mean it runs cooler than the leading competitor 9.0 Ah battery pack under a constant discharge. This is the battery for FLEXVOLT power and long runtime.