There are 16 of P/N 12368082 high performance hardened steel rocker arms in this kit and they have elongated slots to provide extra clearance with high lift (600") camshafts. These rocker arms can be used in all 454 and 502 crate engines and all performance cylinder heads. The have an H stamped on the rocker arm. For a single replacement rocker arm use P/N 12368082. Technical Notes: These adjustable rocker arms are used on the 502/502 crate engine. They can be used on any Mark IV design engine. They can also be used on any Gen V or VI design engine by using rocker stud kit P/N 12495518. Rocker arm P/N 12368082 includes one rocker arm P/N 3959182, one rocker ball P/N 12338047, and one rocker arm nut P/N 3896648.