You should know that ARP uses a premium grade 8740 alloy that is rated far superior to "aircraft" quality. Each stud is precisely heat-treated to 200,000 psi. Following heat-treat, each stud is centerless ground to make it as close to perfectly concentric as possible. Its important to note because lesser quality stud are not centerless ground, but thread-rolled in bar stock form(mostly before heat-treat, when the material is easier to machine). Because ARP studs are manufactured to such exacting tolerances, you will note that gaskets and cylinder heads literally glide into position and are perfectly aligned - something that won;t happen with inferior quality head studs.

ARP studs are thread rolled after heat-treat, which gives them about 1000%(that's ten times) better fatigue strength than those rolled prior to heat-treat.