Get All Power, No Gas with the Hyper Tough 4.0Ah Battery. This 4.0Ah battery is compatible with all Hyper Tough 20V outdoor tools. You will never run out of runtime while having this additional Hyper Tough Battery on hand Lithium-Ion Batteries have a high energy density which provides a longer discharge time and provides consistent power through the charged cycle. Unlike NI-Cad batteries which slow down as energy is depleted, these Lithium-Ion batteries run at full strength until all energy is expended. Once charged Lithium-Ion batteries also have a longer shelf life and will not lose power when not in use. This new battery is sold as a single battery and does not include a charger or a tool. HT21-401-003-11