Rectangular hollow section: Material: Q235, Q345, 20#, ST37, ST44, ST52, ASTM A53, ASTM A106 Rectangular hollow section:1.Item: square ... .Standard: GB, ASTM, BS, JIS, 3.Material: Q195, Q215, Q235, Q345B, X42, Gr. B4.Specification: OD: 15*15mm-400*400mm, WT ...