Split Lock Washer Finish Black Oxide Material Steel For Screw Size 5/16 in Inside Diameter 0.314 in Outside Diameter 0.567 in Maximum Thickness 0.056 in Minimum Thickness 0.056 in Color Black Dimensional Standards ASME B18.21.1 Material Grade/Class Not Graded Pack Size Small Pack Rockwell Hardness C38 System of Measurement Inch Thickness Tolerance +0.010 in Package Quantity 100