The HART 20V 4.0Ah Lithium-Ion battery is an addition, or start to, any DIYers HART tool collection. This battery is compatible with all HART 20V power tools. It features Lithium-Ion technology to give you long-lasting and fade-free power to get you through any project you decide to take on. This battery is designed to be compact and lightweight for more maneuverability and while reducing user fatigue