Ysteel alloy, forging, mil-s-890, alloy 3; 6.880 in. Largest od, 4.940 in. O/a h; with twelve holes, 0.406 in. Dia, equally spaced on a 5.560 in. Diameter bolt circle; with three holes, 0.312 in. Dia, equally spaced on a 5.560 in. Diameter bolt circle