Lock Washer Lock Washer Type Internal Tooth Lock Finish Black Oxide Material Steel For Screw Size 1/4 in Inside Diameter 0.256 in Outside Diameter 0.5 in Maximum Thickness 0.035 in Dimensional Standards ASME B18.21.1 Material Grade/Class Not Graded Pack Size Small Pack Rockwell Hardness C40 to C50 System of Measurement Inch Package Quantity 100