Tap bolts or tap screws are a hex head bolt with a fully threaded shank. They are used in drilled and tapped holes instead of a stud and nut. 18/8 stainless steel is comprised of 18% chromium and 8% nickel. The chromium binds oxygen to the surface of the product to protect the iron from oxidation (rust). Type 316 steel is an austenitic chromium-nickel stainless steel that contains between two and three percent molybdenum. The molybdenum content increases corrosion-resistance, improves resistance to pitting in chloride ion solutions, and increases strength at high temperatures.