Countersunk screw Pro Bolt Made of 316 stainless steel, which offers the following benefits: - excellent strength - excellent corrosion resistance - high resistance to acids The offered stainless steel screws are all polished to a high gloss.    Stainless steels are iron alloys with a minimum of 10.5% chromium added to other elements (nickel, molybdenum, titanium, copper, carbon, nitrogen) to increase properties such as formability and strength. A chromium-rich oxide layer gives stainless steel its corrosion resistance.