The DCB606 FLEXVOLT 20V/60V MAX 6.0Ah ( With DCB606 FLEXVOLT battery when used with DEWALT 20V MAX tools compared to DCB201 1.5 Ah battery pack.) Battery pack changes voltage when you change tools, powering a line of powerful 60V MAX tools, 120V MAX tools, and backwards compatible to existing 20V MAX tools and chargers. The battery pack is smart enough to know when to provide runtime for 20V MAX tools (6.0Ah) and power in 60V MAX and 120V MAX tools