Aluminum alloy qq-a-225/9 7075-t73, anodic type 2 coated, 3.2425in. Min. To 3.2428 in. Max dia, 0.8120 in. Min to 0.8125 in.Max thk, machined surfaces as noted 16.0 32.0 and 125.0 microinch finish, 2 holes0.261 in. Diameter by 0.590 in. Deep tapped 1/4-28 3b thd