The Empi dual purpose oil filler and breather box includes and system of internal baffles that separate the oil from the air, then returns the oil back to the engine. It mounts upright on the alternator stand making for easy oil filling and was designed to look like part of the engine. The billet aluminum filler cap seals with and o-ring. Aluminum construction offers great looks and leak free operation, an o-ring seal, and button headed allen top screws. Vent your valve covers, crankcase, air clearers, whatever your requirements. Comes with attaching nut, O-rings, gasket and instructions. There are 4 threaded ports and all at 1/4" NPT.