Aluminum alloy, qq-a-250/11, composition 6061, temper t6, 3.08 in.Min, 3.14 in. Max lg, 2.65 in. Min, 2.70 in. Max w, four 0.267 in. Min, 0.175 in. Max diameter mtg holes spaced 2.165 in. Min, 2.175 in. Maxby 2.650 in. Min, 2.660 in. Max c to c, 0.062 in. Min, 0.072 in. Maxthk cover