Exclusive 12-point head, with special shouldered "stop" to hold the wrench, eliminates the need for special adjusting toolsForged in-house from grade A 8740 alloy chrome moly steel and heat-treated throughout for a 190,000 psi tensile strength, not simply case hardened like others areThreads are precision CNC-machined exactly perpendicular to the bottom of adjuster to ensure an optimum seat, even pressure, and maximum engagementBottom is flush-ground perpendicular to the threads, so it seats evenly, and the set screw has flush-machined tip for optimum contact and seating on studDesigned for aluminum rockers, and features an overall length of 1.200, a thread size of 7/16 - 20, and a body diameter of .550; sixteen adjusters per packageOne of the more aggravating things found in many high performance engines is constantly having to re-adjust rocker arms. Until ARP introduced the patented Perma-Loc rocker arm adjuster, there wasn't a "poly lock" on the market that you didn't have to continually tighten. There are several important reasons why ARP's exclusive Perma-Loc rocker arm adjusters won't loosen like others. First, the adjuster body is heat treated all the way through (not simply case hardened), which eliminates the thread "movement" common to others. Secondly, the threads are machined exactly perpendicular to he bottom of the adjuster, so it seats evenly and applies pressure on a full 360 degree circle. Lastly, the set screw is machined flush on the bottom, not pointed, so it will have optimum contact on the rocker arm stud. Perma-Loc adjusters are also easy to use, because the compact 12-point head is designed to hold your wrench in position while you lock the set screw with an Allen wrench.
