These head studs are manufactured by ARP from premium 8740 chrome moly steel and heat treated to 200,000 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 and 12 point nuts included. Exact tolerances ensure that gaskets and cylinder heads just glide into position and align perfectly. For all 2004 and newer LS engines, including LS1 and LS6.