steel tube according to ASTM A53, DIN 2394, DIN2395, BS1387,ASTM A500. for structure and transferring water and gas. UL certs Steel tube,including ERW and Seamless, 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, EN39(BS1139), DIN2440/DIN2444, JIS G3444, BS1387, DIN2394, ...