DIN2391 NBK then galvanized EN10305-1 NBK then galvanized For hydraulic use High precision and smoothness for inside of the tubes. Size:4-280mm WT:1-50mm Steel Grade: ST35,ST37,ST37.4,ST52, E215,E235,E355 24CrMo4,24CrMo,35CrMo4,35CrMo,2 0Cr Richard Shen Ningbo New-Era Steel Tube Co,.Ltd Tel: 0086-574-87334900 Fax: 0086-574-87715158 Mobile: 0086-(0)137 3616 4628 Email: Richard831228@gmail.com Msn: Richard831228@hotmail.com Skype ID: Richard831228