Flat Washer Flat Washer Type Standard Dimensional Standards DIN 125-1A Material Steel Material Grade/Class Grade 2 Finish Black Oxide 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 Clear Inside Diameter Tolerance 0.827-0.84 Made in North America No Manufacturer Location Globally Sourced Material Quality Standards Not Rated Maximum Temperature 350 Degrees C