Structural Flat Washer Flat Washer Type Standard Material Steel Material Grade/Class Grade 2 Finish Black Oxide For Screw Size 5/8 in Inside Diameter 0.172 in Outside Diameter 1 5/16 in Maximum Thickness 0.177 in System of Measurement Inch Minimum Thickness 0.11 in Material Quality Standards ASTM F436 Pack Size Bulk Pack Rockwell Hardness C38 RoHS Compliant No Thickness Tolerance - Package Quantity 1000