【Premium Material】The quick-release internal tooth metal washers are made of 65 manganese steel. They are sturdy and durable, do not deform, are resistant to abrasion and corrosion. They are durable. Starlock washers exert a spring force between the head and the substrate. 【Practical Tool】Self-locking washers are ideal for quick repairs. They exert a spring force between the mounting head and the substrate, which reinforces the washer against the substrate. They provide better resistance to friction and rotation. 【Various Sizes】The lock washers are available in 7 most common sizes: M3, M4, M5, M6, M8, M10 and M12 Starlock. You can choose different sizes according to your needs. 【Wide Application】Washer range widely used in many fields, e.g.: machinery, lawnmowers, engines, cars, trucks, trailers, toys, bicycles, RVs, boats, pumps, furniture, etc. 【Package Contents】The fastener assortment kit contains 340 black lock washers in a plastic box. Each size is individually separated in the