Barrel Screw Guaranteed last 1 year Based Material:38CrMoAlA,42CrMo,SKD61,DC53,SKH55,GH113 Surface roughness:Ra 0.4 um Alloy depth:2-5 mm Hardness after nitriding:HV950-1200 Depth of nitrided layer:0.6-0.9mm Alloy hardness:HRC62-68