There are many important reasons to use ARP main bolt sets, including eliminating main cap and frets, as well as protecting the threads in your engine block. The studs are manufactured in their own factory using the best processes, designs, materials and engineering. Each main bolt set exceeds the most stringent aerospace specifications and comes complete with hardened parallel ground washers and aerospace nuts. The studs are made of 8740 chrome moly steel, and heat treated to 200,000 psi tensile strength. J-shape threads are rolled after heat treatment to create a fastener that is threads 1000% stronger than others. Note that although ARP produces both bolts and bolts, they recommend using main bolts over bolts whenever possible for multiple key reasons. First, the ability to get more accurate torque values as the bolts do not "twist" into the block. All clamping forces are on one axle. By the same sign, less force is applied to the block threads, which contributes to an improved service life (which is very critical for aluminium blocks). They also allow for easier engine mounting and correct alignment of caps every time.