Description High quality materials: 65mn metal steel black oxide surface treatment without burrs, with good corrosion resistance and high temperature properties. Wide range of applications: these internal tooth washers are suitable for automotive manufacturing , marine equipment, machinery and equipment, medical equipment, mining equipment, shock absorbers, bearings and machinery. Product features: the lock washer exerts an elastic force between the head of the fastener and the base body, so that the washer barely touches the base body, while the bolt thread is firmly seated against the nut or the base body thread, creating more friction and resistance to rotation. Practical tools for daily use: the pack contains 50 mounting washers, each with a diameter of 3 mm. They are very practical and you can replace your old seals in time.