Premium Material: Starlock internal tooth washers are made of high quality 65Mn metal steel, which is a black oxide coating on the metal surface for protection against rust, corrosion and durability. It has high hardness and good toughness that is not easily deformed during use. It can normally be locked onto materials such as plastic and steel. Easy to Use: The fast-rotating clamping discs exert a spring force between the fastener head and the substrate, which keeps the washer firmly fixed and creates more friction and resistance to rotation. Easy to Store: All the locking rings in the range are packed in a strong transparent plastic case, which is easy to use, 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 enthusiasts, electrical appliances, electronics, automobiles, sports equipment and industry. For example, to repair ice machines, lawn mowers, tricycles, toys, old pinball machines, golf bag holders, stroller wheels, tractor emblems and repair a barbecue, etc. Package Contents: You will receive 340 pieces of lock washers in sizes M3, M4, M5, M6, M8, M10, M12, suitable for different sizes of fasteners, enough for your daily use. Package Contents: ? 50 pieces M3 x 8. 50 pieces M4 x 12. 50PCS-M5x12. 40 pieces - M6 x 14. 40 pieces - M7 x 15. 40 pieces - M8 x 18. 40 pieces - M10 x 20. 20 pieces M12 x 25. 1 storage box