1. 2.Made of 65Mn metal steel, anti-corrosion and 3.A Lock washer exerts a spring force between the fasteners head and the substrate to create more friction and resistance to rotation 4.7 size of M3 M5 M6 M8 M10 M12 total 340pcs in a transparent box, applicable to different sizes of fasteners 5.Widely used in machinery equipment, industrial production of shock absorption and insulation,can meet your different needs in Size:M3,.,M5,M6,M8,M10,M12 Material:Metal steel colour:black Package Contents: 60 * M3 lock washer 60 * lock washer 60 * M5 lock washer 50 * M6 lock washer 50 * M8 lock washer 40 * M10 lock washer 20 * M12 lock washer Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.