... spring steel ,stainless steel,carbon steel,etc Surface: Zinc plated or Black Size: M6-M100(1/4-4inch) Features: 1.Flat washer and ... MaterialCarbon steel,45#,65Mn,stainless steel,brass4.FinishPlain;black; zinc plated(Cr,3+);zinc plated(Cr,6+); hot dipped galvanized; dacromet ... strict quality control from producing to delivery. Stainless steel/galvanized steel spring washer and flat washer,tapper washer