This is a Newbeat 21V 4000mAh Lithium-Ion battery designed for use with cordless power tools.
Key Specifications
Voltage: 21V
Capacity: 4000mAh (4.0 Ah) for extended run time
Power Type: Rechargeable Lithium-Ion
Compatibility: Fits Newbeat 21V cordless tools and standard Makita-style 21V tool bases