Lock Washer Lock Washer Type Internal Tooth Lock Finish Plain Material Phosphor Bronze For Screw Size 1/2 in Inside Diameter 0.53 in Outside Diameter 0.9 in Maximum Thickness 0.045 in Color Bronze Dimensional Standards ASME B18.21.1 For Use With Large Round Pan or Binding Head Screws Material Grade/Class Not Graded Pack Size Small Pack Rockwell Hardness B90 System of Measurement Inch Thickness Tolerance 0.037 in to 0.045 in Package Quantity 25