Precision Cold Drawn Seamless Tube/Ready to Honed Tube/Pre-honed Tube Grade: ST 52,ST52.3,CK45,E355,16Mn,STKM13C,SAE1020 Precison Cold Drawn Seamless Tube/Ready to ... Honed Tube/Pre-honed TubeGrade: ST 52,ST52.3,CK45 ... to 0.6mm.ID Roughness(Ra): < 1.6 Micron Precision Cold Drawn Seamless Tube