steel mil-s-6049 cond c-1; 2.375 in. od; 0.694 in. thk; 1.375-18 unef-3b thread; 4 equally spaced flanges on periphery 0.250 in. wide 0.075 in. thk with holes 0.0475 in. thru flange thk; 4 equally spaced 0.250-28 unf-3b threaded holes between flanges on periphery