Premium Material: Starlock Inner Tooth Washers are made of high quality 65Mn metal steel, which is black oxide coating on the metal surface for rust protection, corrosion protection and durability. It has high hardness and good toughness which is not easily deformed during use. It can normally be locked onto materials such as plastic and steel. Easy to use: Rapidly rotating clamp discs exert a spring force between the fixture head and the substrate, which which keeps the washer firmly fixed and creates more friction and resistance to rotation. Easy to store: All safety rings in the range are packaged in a strong, easy to use clear plastic case , to find and carry and can also be used as a storage box. Wide applications: these Starlock washers are widely used for machines, furniture, tables, DIYers, 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 barbecue grill, etc. Contents of Delivery: You will receive 340 pieces of safety washers in sizes M3, M4, M5, M6, M8, M10, M12, suitable for different sizes of fasteners, enough for your daily use. Scope of delivery: ? 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