We currently offer three types of A1 Technologies Performance Racing Fasteners. They are 17-22A, H-11 and 625 Plus Custom Aged Alloy. The performance diesel head studs that are offered in these alloys are for the RAM Cummins and Ford Powerstrokes. The difference between the different materials is the strength, corrosion resistance and manipulation to excessive heat. The highest rated in strength is the 625+ custom aged alloy at around 260,000 psi tensile strength, next is the H-11 at an approximated 250,000 psi tensile strength and then 17-22A alloy being a significant step above the factory head bolts in clamping and stretch resistance at around 200,000 psi tensile strength. Our lineup of A1 Technologies performance diesel head studs for Ford Powerstroke and Dodge Cummins is a great place to complete your buy.