Lock Washer, Lock Washer Type External Tooth Lock, Finish Zinc Plated, Material Steel, For Screw Size 1/4 in, Inside Diameter 0.267 in, Outside Diameter 0.51 in, Maximum Thickness 0.028 in, 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 C38 to C46, System of Measurement Inch, Thickness Tolerance 0.023 in to 0.028 in, Package Quantity 100.