Split Lock Washer, Lock Washer Type Split Lock, Finish Black Oxide, Material Steel, For Screw Size #4, Inside Diameter 0.114 in, Outside Diameter 0.209 in, Maximum Thickness 0.025 in, Minimum Thickness 0.025 in, Dimensional Standards ASME B18.21.1, Material Grade/Class Not Graded, Pack Size Small Pack, Rockwell Hardness C40 to C50, Package Quantity 100 Split lock washers apply greater bolt tension per unit of applied torque to help prevent rotation and loosening. Meet ASME B18.21.1 standards.