Aluminum alloy 6061-t6 qq-a-250/11, anodize mil-a-8625 type ii, fifty-one holes 0.281 to 0.289 in., four holes 0.220 to 0.228 in., fifty-one self-locking nut plates 1/4-28 unjf with a domed floating nut, four self-locking nut plates 10-32 unjf with a domed floating nut