Premium Material: Starlock internal dental washers are made of high quality 65Mn metal steel with black oxide coating on the metal surface, which is anti-rust, anti-corrosion and durable. It has high hardness and good toughness and is not easily deformed during use. It can usually lock onto materials like plastic and steel. EASY TO USE: The quick-turn chuck applies spring force between the fastener head and the base material, holding the joint firmly in place and creating more friction and resistance to rotation. EASY TO STORE: All the locking rings in this series are packed in a sturdy transparent plastic box, which is easy to use, find and carry, and can also be used as a storage box. Wide Application: These Starlock washers are widely used in machinery, furniture, tables, DIY, electrical, EE, automotive, sports equipment and industry. Examples include repairing ice machines, lawn mowers, tricycles, toys, old pinball machines, golf bag brackets, stroller wheels, tractor panels, and