Aluminum alloy, qq-a-250/4, alloy 2024, t3; finish: anodized, mil-a-8625, type 2; 0.125 in.Face w; 2.104 in. O/a lg; 0.500 in. Bore dia; three unthd holes equally spaced on a 0.875 in.Bolt circle dia, one hole 0.093 in.Dia, two holes 0.128 in.Dia through counterbore 0.234 in.Dia x 0.060 in.D