This is an OEM Subaru compressor bypass valve, otherwise known as a blow-off valve. Is your car not making the boost that it should? A defective CBV might be the culprit.
Comes with new gasket pre-installed.
Fits all 2008-2014 Subaru WRX. (The 2008 WRX actually uses the Legacy GT-style valve, but this one will be slightly louder.)
