Flat Washer Flat Washer Type Standard Dimensional Standards ANSI B18.22.1 Material PEEK Material Grade/Class Grade 2 Finish Plain For Screw Size M20 Inside Diameter 21 mm Outside Diameter 37 mm Maximum Thickness 3.5 mm System of Measurement Metric Minimum Thickness 3.5 mm Color Brown Maximum Temperature 500 Degrees F Minimum Temperature -50 Degrees F Pack Size Small Pack Rockwell Hardness D87.5 Thickness Tolerance +/-0.5mm Package Quantity 10