The DeWalt XR FLEXVOLT is a 18/54V convertible battery pack System perfect for professional use as a 54V Battery has unprecedented levels of power, finally giving you the power you need from a cordless tool. That's not all though - it can switch itself to 18v so it is compatible with your existing 18v XR power tools offering extended runtime, meaning you don't need to replace your existing kit - not even your 18v XR charger, as these batteries are compatible! The FLEXVOLT range includes a host of top-performing powerful, brushless and cordless tools powered by either a single 54v FLEXVOLT battery, or twin batteries to give the power of a corded tool. This battery has the same width and length of a 18v XR battery, with only a small increase in height - so its not even going to get in your way. This is supplied as a single battery.