The HART 20V 4.0Ah Lithium-Ion Battery is an excellent addition, or start to, any DIYer’s 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. Whether you are maintaining your yard with HART outdoor tools, cleaning and maintaining your car with HART automotive tools or keeping cool and entertaining with HART lifestyle tools, the HART 20V 4.0 Ah battery is there to provide the power you need when you need it with 4x longer runtime than the HART 20V 1.5 Ah Lithium-Ion battery.