There are many reasons to use ARP main stud kits, including the elimination of main cap walk and fretting, as well as protecting the threads in your engine block. All kits come complete with parallel ground washers and high quality nuts. Includes provision for windage tray and serrated locking nuts. The studs are manufactured from 8740 chrome moly steel, heat treated in house to 200,000 psi tensile strength, and precision J-form threads rolled after heat treat to create a fastener that has threads 2000% stronger than others. Fits all OEM LS engine blocks and most aftermarket blocks.