steel tube according to ASTM A53, DIN 2394, DIN2395, BS1387,ASTM A500. for structure and transferring water and gas. UL certs ... , round and rectangular or square, aew according to standards ASTM A53, ASTM A106, ASTM A795, ASTM A135, ASTM A500, API 5L, API5CT, UL6, UL797, EN10219, EN10255, EN10240 ...