ARP Studs are thread rolled after heat-treat, which gives them about 2000% (that's twenty times) better fatigue strength than those studs that are threaded prior to heat-treat (a very common industry practice). It costs a lot more to do it this way, because it's tough on tooling.
Specification:
Overview:
These Pro series studs from ARP are cold-forged to ensure molecular integrity. They are heat-treated prior to thread rolling and machining and are rated at a whopping 190,000 psi. The Pro series kits are also available with 12-point nuts, and all kits come complete with hardened parallel washers for an even load distribution and accurate torque readings.