Engineered for your special application, ARP pressure plate bolt kits are the finest available and feature a large diameter, low profile head. Includes hardened washers. ARP High Performance Series bolts are made from a premium grade chrome moly and hardened to a nominal tensile strength of 180,000 psi. The Pro Series bolts, originally developed for NASCAR competition, are stronger and rated at 200,000 psi. 6/pkg.