1aluminum; anodize finish; 3.500 in. Od; 0.957 in. Id; 1.812 in. Diameter counterbore one end, 1.124 in. Diameter counterbore other end; 2.248 in. Diameter of hub; 6 holes 0.180 drill through countersink, 0.360 in. Dia, equally spaced on 2.940 in. Diameter bolt circle