The DEWALT FLEXVOLT 20/60V MAX Battery 6.0AH (DCB606) 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 the new 60V MAX and 120V MAX tools.