One of the more aggravating things found in many high performance engines is constantly having to re-adjust rocker arms. Fact is, up until ARP® introduced the patented Perma-Loc™ adjuster, there wasn’t a “poly lock” on the market that you didn’t have to keep after. 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 just case hardened). This eliminates the thread “movement” common to others. Secondly, the threads are machined exactly perpendicular to the bottom of the adjuster, so it seats evenly and applies pressure on a full 360° circle. Lastly, the set screw is machined flush on the bottom (not pointed) so it will have optimum contact on the rocker arm stud. You’ll find ARP® Perma-Loc™s easy to use, too. The compact 12-point head is designed to hold your wrench in position while you lock the set screw with an Allen wrench. With most “poly locks” you have to invest in a special tool to do the job. All in all, they’re the best you can buy!