Pro series cylinder head 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 200,000 psi for the 8740 material and 220,000 psi for ARP2000. ARP 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.