From the Manufacturer The Worx 18-volt lithium-ion replacement battery is designed for use with battery Worx WG151 developed models. 5, WG251. 5 and WG540. It is ultra lightweight, fast charging, and provides prolonged duration than standard NiCd batteries. 18V Li-Ion battery repl. 18V / 1 3AH Li-Ion Battery for Worx WG151 model. 1 battery lawn trimmer. Read customer review 