Ribbed Safety Lock Washer / Knurl Washer DIN 9250S: M1.5~M36. VS: M5~M30. Normal or thicker thickness.Material: Spring steel Mn65 / C67S / C70.Stainless Steel ANSI 420, 304, 316.Surface Finish: Black Phosphating, Black Oxide, Zinc plating, Dacromet, Plain. Size, thickness, style or other specifications can be designed according to your demand.