The DEWALT DCB606 FLEXVOLT Battery pack changes voltage when you change tools. It Powers a new line of 60V Max Brushless tools and 120V Max Brushless tools. This pack is also backwards compatible with 20V Max tools and chargers. The FLEXVOLT® 20V/60V MAX* 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.