Flat Washer Flat Washer Type Standard Dimensional Standards DIN 125-1A Material Steel Material Grade/Class Grade 2 Finish Plain For Screw Size M20 Inside Diameter 21 mm Outside Diameter 37 mm Maximum Thickness 3 mm System of Measurement Metric Minimum Thickness 3 mm Color Black Pack Size Small Pack Thickness Tolerance +/-0.30mm Package Quantity 25