If you have ever installed a rocker stud into a cylinder head and watched it wobble as it screwed in you knew from the beginning that the rocker geometry was going to be inconsistent all over the place. ARP rocker studs are concentric within .005 T.I.R. thread pitch to thread pitch. They run-in straight and true. Lengths are exact designed to provide positive seating every time. An extra-large radius base offers greater resistance to flex. Available in both High Performance and Pro Series models. NOTE Not to be used with OEM-style, self-locking nuts. To be used with ARPs patented Perma-Loc adjusters. HIGH PERFORMANCE SERIES Made of 8740 chrome moly forgings and heat-treated to 180,000 psi. Excellent for E.T. Bracket Racing, limited rule oval trackcompetition and street use. Tip ground flush for optimum adjuster seatin. PRO SERIES Designed for competition applications, ARPs Pro Series rocker arm studs are made of premium grade 8740 chrome moly steel and heat-treated to a tensile strength of 200,000 psi. IMPORTANT TECH NOTE It is highly advisable to determine what the optimum rocker arm stud length is for your particular application. This is especially true when long pushrods and valves are employed you should raise the installed height of the rocker arm to compensate for the longer-than-stock components. Rocker Arm Studs High Performance Series Shank Under Hex to Locate Guide Plate 2Pieces Adjuster Thread Depth 0.85 Base Dia/Thread 7/16-14 Screw-In Thread Depth 0.8 Shank Dia/Thread 7/16-20 Stud Height 1.75