Aluminum alloy, qq-a-225/8, alloy 6061, t6, anodized, mil-a-8625, type 1, hardness 45 rb min, 1.372 in. Min, 1.373 in. Max od, 0.635 in. Min, 0.645 in. Max h, 2.480 in. Od of flange, four 0.189 in. Min, 0.194 in. Max diameter holes equally spaced on 2.100 in. Diameter bolt circle