Premium Material: Starlock internal tooth washers are made of high quality 65Mn metal steel, whose metal surface is treated with black oxide coating for anti-rust, anti-corrosion and durability. It has high hardness and good toughness, and is not easily deformed during use. It can be fixed on materials such as plastic and steel normally. Easy to Use: Fast rotating clamp washers apply spring force between the fastening head and the substrate, which firmly fixes the washer and creates more friction and rotation resistance. Easy to Store: All series safety rings are packed in a sturdy, easy-to-use clear plastic case, which is easy to find and carry, and can also be used as a storage box. Wide Applications: These starlock washers are widely used for machinery, furniture, tables, DIY, electrical appliances, electronics, automobiles, sports equipment and industry. For example, for repairing ice cream machines, lawn mowers, tricycles, toys, old pinball machines, golf bag holders, stroller