Steel alloy, mil-s-13326, plate form, class 100, condition a/a, 3/4 in. Thk material, 5 in. W by 6 in. Lg base, four 11/16 in. Diameter mtg holes spaced 3-1/4 in. C to c on w and 4-1/4 in. C to c on lg of base, 4-1/4 in. H tongue w/attachment hole 1-1/16 in. Dia