Flat Washer Flat Washer Type Standard Dimensional Standards ASME B18.5 ASTM F-436 Material Steel Material Grade/Class Grade 2 Finish Zinc Yellow For Screw Size 1/4 in Inside Diameter 0.313 in Outside Diameter 3/4 in Maximum Thickness 0.066 in System of Measurement Inch Minimum Thickness 0.066 in Color Yellow Pack Size Bulk Pack Rockwell Hardness RC38 Thickness Tolerance +/-0.145 in Package Quantity 6500