Lock Washer Lock Washer Type Internal Tooth Lock Finish Zinc Plated Material Steel For Screw Size 5/16 in Inside Diameter 0.32 in Outside Diameter 0.59 in Maximum Thickness 0.04 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