Far superior to any other main bolts available for use in competition engines, ARP main bolts are designed to meet the exacting standards and demands of professional engine builders. Forged from 8740 chrome moly steel, all ARP main bolts feature a reduced renching head, large underhead radius and rolled threads for the utmost in reliability. The threads are rolled after heat-treating which gives them about 2000% better fatigue strength than most main bolts that are threaded prior to heat-treating. The popular High Performance Series is rated at 180,000 psi, and is a premium replacement for OEM fasteners. Pro Series main bolts are application-specific, rated at 190,000 psi, and designed for use in competition engines. Hardened parallel-ground washers are included with each kit.