These late model valve cover fill caps screw into the valve cover like an ordinary cap. These caps feature a baffle & -10 ORB (7/8"-14 Straight Thread O-Ring Style Port) for use w/ AN O-Ring Fitting (or Port hose end) & AN hose to the catch tank or PCV. These caps eliminate the need to modify your valve covers when adding a catch tank to your racing engine (required by most sanctioning bodies in racing applications). Choose from two versions w/ one that fits factory valve covers (GM LS, GM Gen-V LT, & Ford Coyote Gen1-Gen2), and the second version that fits Holley Cast Aluminum GM LS Valve Covers. Billet aluminum construction w/ black anodized finish. Use w/ ORB (O-Ring Boss) hose end AT849010ERL, O-Ring Boss to AN Flare Adapter AT985010ERL (straight), or AT949010ERL (90 Degree) & AN hose to the Catch Tank.