Flat Washer Flat Washer Type Standard Material Stainless Steel Material Grade/Class 18-8 Finish Plain For Screw Size M12 Inside Diameter 13 mm Outside Diameter 22 mm Maximum Thickness 3 mm System of Measurement Metric Minimum Thickness 3 mm Inside Diameter Tolerance +/-0.010 in Material Quality Standards ASTM A582 Outside Diameter Tolerance +/-0.010 in Pack Size Small Pack Resistance Properties Chemical Resistant Corrosion Resistant Rockwell Hardness B83