Steel, mil-s-18729, comp 4130; cadmium and chromate, qq-p-416, type 2, cl 2; rockwell hardness c scale, 35.0 min to 39.0 max; 0.319 in. Min and 0.329 in. Max id; 0.500 in. Min and 0.520 in. Max od; has internal key 0.041 in. Lg and 0.055 in. W; 0.110 in. Thk; has 0.067 inches diameter locking wire hole