Hollow Section Specification: Q195, Q235, SS400, A500 Gr. A/B Sizes: 20 x 20~500 x 500mm, thickenss 1.0-20mm Hollow Section Specification: Q195, Q235, SS400, A500 Gr. A/B Sizes: 20 x 20~500 x 500mm, thickenss 1.0-20mm 20 x 30~600 x 500, thickenss 1.0-20mm square hollow section