These special fittings allow easy installation of a catch tank on GM LS racing engines that have a PCV (positive crankcase ventilation) fitting on the OE valve cover. This fitting has a 3/4" outside diameter that fits into the OE grommet instead of the stock PCV fitting. Choose from fittings with -8 AN or -10 AN male flare. Ideal for use in racing applications that require the use of a catch tank.