... /12.9 4.case hardening:HRC38-HRC42 raw material40Cr,35CrMosize1/2''--1.1/4,M12--M36Colorblackgrade10.9/12.9handnessHRC35-42(BOLT),HRC29-36 ... spring nuts, T nuts, K nuts, rivet nuts, cage nuts, lock nuts, hex nuts, hex flange nuts, wing nuts, weld nuts ... , square nuts, cap nuts.Washers: flat washers, spring washers, lock washers, structural Washers. square washer, bowl washer.Screws: machine screws ...