Features: This 5S 21V 2MOS lithium batteries protections board delivers high efficiency and robust safety with overcharge and over discharge protections, perfect for 21V electric tools requiring reliability power management. Featuring a 2MOSFET design with low on resistance, it ensures stable charging and discharging performances while minimizing heat generation for enhanced durability in various applications. Ideal for enthusiasts and professional building battery packs, especially for electric tool and similar devices, ensuring safe and efficient power solution. Designed for seamless integration into electric tool and projects like creating replacement batteries, it use in high voltages scenario such as power tool maintenance and upgrades. With its compact size, clear wiring labels, and strong compatibility, this protections board simplifies installation and enhances versatility in electronic assemblies for extended battery life. Specifications: Component: PCB, metal Size:Approx.46x40mm Product type: 5S 21V 20A Option Type:1pc,3pcs; for Power Tool Applicable scenario:battery pack production,Power tool modification, Package Includes: Package A 1pc Battery protections Board Package B 3pc Battery protections Board 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.