... We strictly execute precision tube production standard, each production stage can be traced in the record.Standard: DIN2391, EN10305-1, EN10305-3.Steel ... grade: ST35, ST37, ST45, ST52, E235, E355.Tube OD: 5-80mmTube WT: 1.5 ... -8mmCondition: BK, BKW, BKS, NBK, GBK.Management standard: ISO9001:2000, TS16949. ...