Countersunk Washer Material Grade/Class Not Graded Material Steel Finish Black Oxide For Screw Size M6 Maximum Inside Diameter 6.4 mm Outside Diameter 32 mm Countersink Angle 90 Degrees Overall Height 4 mm System of Measurement Metric Color Black For Use With Flat and Oval Head Screws Industry Standards AMPG 2002 FIN.31 Pack Size Small Pack Rockwell Hardness C40 Thickness Tolerance +/-0.3 mm