The Mishimoto WRX oil catch can is designed and engineered to eliminate harmful blow-by vapors from re-entering your engine. The EJ25 in the STI is known for producing blow-by gases during both normal and severe driving, especially when boost levels are increased. This oil blow-by can work its way into your intake system, reducing the octane rating of your fuel and potentially causing detonation. The system uses both of our patent pending 2-Port Compact Baffled Catch Can and 3-Port Compact Baffled Catch Can, each with a 50-micron bronze filter and an internal baffle to better separate the oil from the crankcase vapors. The turbo inlet side of the kit utilizes our 3-port baffled catch can to catch as much oil vapor as possible. The system also includes two direct-fit mounting brackets that are extremely easy to install and also fit right hand drive vehicles.