Exact tolerances ensure that gaskets and cylinder heads just glide into position and align perfectly. ARP Head Studs are available with hex or 12-point nuts. These head studs are manufactured by ARP from premium 8740 chrome moly steel and heat treated to 190,000 psi. They are thread rolled after the heat treating process, which vastly improves their fatigue tolerance compared to studs threaded before heat treatment. High-quality, parallel ground washers included.