ARP 5359601 Stainless 300 Hex Engine & Fastener Kit Contains 12 groups of fasteners, virtually everything you need to assemble a show-quality carbureted engine All neatly organized and labeled in protective vacuum-wrapped packages Manufactured from polished Stainless 300 steel, a proprietary alloy that is impervious to rust and corrosion Heads are traditional hex style, and premium-quality washers are included Rated at 170,000 PSI, which is considerably stronger than Grade 8 hardware