Lock Washer Lock Washer Type Internal and External Tooth Lock Finish Zinc Plated Material Steel For Screw Size 1/2 in Inside Diameter 0.512 in Outside Diameter 1.38 in Maximum Thickness 0.052 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 25