Knurled nut: high quality brass material, RoHS environmental protection Type: M3 Size: 8 * 3 * 5 outside diameter Copper nuts have the advantages of not rusting easily, being resistant to corrosion, being easy to conduct heat, and having strong electrical conductivity. They are generally used in anti-rust, high-temperature, electrical, and heat-conductive Environments such as faucets, valves, electrical switches, etc.