This is a plug I designed to cap off the OEM Subaru PCV electrical connector when you remove the “sensor”, typically when installing an AOS or when cleaning up the engine bay. You end up pulling the jumper from the white hose/electrical connector “sensor” and inserting it into the grey connector to prevent throwing a CEL. These really have no function that I can to let you know it's disconnected which would be a massive vacuum leak. Most people just tape up the connector to prevent water from entering but I wanted something cleaner looking that was easily reversible.