"STEEL,SAE 4130; ROCKWELL C45; CADMIUM PLATED; 4.000 IN. DIA; 0.250 IN. H; 0.093 IN. THK; FURNISHED WITH LOCK ASSEMBLY; MARKING ON PLUG OPEN-LOCK; FOUR MTG HOLES,0.312 IN. DIA,EQUALLY SPACED ON 3.250 IN. BOLT CIRCLE DIA; COUNTER SUNK ON ONE SIDE; ONE OFFSET CENTER HOLE 0.560 IN. DIA"