4steel, aisi c1010-c1020, cadmium plate in accordance with qq-p-416, type 2, class 2, 2.286 in. Lg, 2.286 in. W, 0.500 in. Deep, four no. 8/0.164 in./-32unc-2b thd holes on 1.786 in. By 1.786 in. Mtg centers, surface to have 125 microinch finish all over