CFM Performance 1-0201-0-FB Billet Baffled Valve Cover Breather Oil Cap LSx LS1 LS2 LS3 LS6 LS7 (Flat Black) CFM Performance valve cover breather is the ONLY one in the market which incorporates a check ball to keep unmetered air from coming through while the crankcase is under vacuum Acts just like a factory oil cap under normal driving conditions and when you get into boost it will release any crankcase pressure present Note: Breather will not work engines with dry sump