Zaluminum alloy per ams4150, anodize all surface not hard coated, hard coat per ams2468, surface roughness per pratt whitney specification no. Pwa351, 4.110 in. Min, 4.120 in. Max lg, 0.6546 in. Min, 0.6547 in. Max od, 0.2510 in. Min, 0.2530 in. Max id