Features: Premium Replacement Battery Case for BL4020/BL4030/BL4025 delivers secure compatibility for 40V tools and robust protections via built in PCB against overcharge/discharge, supporting 10x21700 cells for highly power applications. Crafted with impacts resistant ABS housing and reinforced metal contacts, this battery pack case features clear assembly guides for effortless customization while maintaining compact portability. Ideal for power tool enthusiasts, makerspaces, and professional seeking reliability aftermarket solution for 40V outdoor equipment and workshop machinery. Note:This is just a battery case, battery not included. When welding, please add full tin. Before use, please keep the single section voltages below 4.0V and activate it with chargers, otherwise it cannot start working Specifications: Component: ABS, Metal, PCB Size:Approx.8.7x6.5x5.6cm/3.43x2.56x2.2inch Color: black Applicable total voltages: 40V Adapted battery: for 10pcs 21700 lithium batteries(not included) Single battery voltages: ≤4V for BL4020/BL4030/BL4025 Power Tool Applicable scenario:power tools,outdoor activities; Package Includes: 1pc Battery Box(Battery in picture is not included) note: Please allow 1-3cm errors due to manual measurement. Due to the differences between different monitors, the picture may not reflect the actual item color. .