Steel, qq-s-624, 2.895 in. Min, 2.905 in. Max od, 1.262 in. Min, 1.272 in. Max diameter center aperture 9 holes 0.534 in. Min, 0.538 in. Max diameter on 1.969 in. Bolt circle, 0.1517 in. Min, 0.1522 in. Max thk, 16 microinch finish on surface of both faces and id of holes on bolt circle