Heat treated 180,000 PSI aircraft alloy steelCenterless ground to remove material imperfectionsRolled threads for the strongest threads periodBlack oxide treated for enhanced corrosion resistance5mm Allen Hex to ease installation and removal (see Figure 2 & 3)KPMI® Cylinder Studs are mad,000 psi yield strength, fine grain, heat treated, aircraft grade alloel. When you want a stud that meets proof-stress and maximizes clamping force, look no further. KPMI® “rolls” the threads, heat treats and then centerless grinds the entre boy of the stud. Rolling the threads creates the toughest and strongest threa possible and centerless grinding removes notch sensitivity. The final process for all KPMI® Studs is to encase the entire stud with premium corrosion resistant treatment of Black Oxide. Congratulations on your choice to purchase a stud that meets and exceeds your stock-replacement of high-performance needs!