There are many important reasons to use ARP main stud kits on your 03-06 Evolution 8 or 9, including the elimination of main cap walk and fretting, as well as protecting the threads in your engine block. Every ARP main stud kit for the Evo 8 & 9 exceeds the most stringent aerospace specifications. All kits come complete with hardened parallel-ground washers and aerospace quality nuts. Some applications have provisions for mounting windage trays and have specially designed standoff studs with serrated lock nuts to position the windage tray and lock it securely in place. The studs are manufactured from 8740 chrome moly steel, heat-treated in-house to 190,000 psi tensile strength, and precision J-form threads rolled after heat-treat to create a fastener that has threads 1000% stronger than others.