HDG steel pipe 1. many different sizes of the products 2..low ... resistant with black paintingAll the production process are made under the ISO:9001-2000 strictly1) Standard:API 5L,ASTM 36.10M,A106,A53 ... ,DIN 1629,1626,BS,JIS.etc2) Material: ASTM A106/A53,ST37,35, API ... ,gas,chemical,power,shipbuilding,boiler,construction,,metallurgy,etc HDG steel pipe