HDG steel pipe 1. many different sizes of the products 2..low ... 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 5L GR. B /X42/X52 ... :petroleum,gas,chemical,power,shipbuilding,boiler,construction,,metallurgy,etc HDG steel pipe