PRW 1530202 Billet Aluminum Stud Girdle with FMS Aluminum Head 7/16" RockerLoc for Ford 351W, Boss Reduces rocker stud flex to retain critical valve lash adjustments Made from 6061-T6 aluminum Relieved at the factory to accommodate crankcase evacuation components without the need to visit your local machine shop Anodized for a superior finish Comes complete with PRW RockerLocs