The manufacturiing standard adopted for this product is DIN2391 standard series, this type of steel tubes can meet the special requirements of high precision and fine finish steel tubes used in various trades, with the mechanical properties suitable to the bending at any angle and capable of bearing all types of high pressure, cold bending,tube end expansion,bruising interlor or exterior wall of the tubes, without causing any blockage to the pneumatic,hydraulic and oil routes.The percentage elongation and the stength of steel tubes are extremely ideal.