... :Alloy casting iron, ductile iron rings;keystone ring, taper ring, drum ring;Chroming ring, spray molybdenum ring.Capacity:40 Millions Pcs/year.2.Plasma Mo ... .These are the barrel surface ring,keystone surface ring,cone surface ring,twist side ring,chromium plating ring,spray molybdenum ring,nitride ring,steel disc rng,as ...