With new and improved styling, the TurboXS RFL blow off valve for the Subaru WRX and STI remains true to it's roots - it's still really loud! Like all TurboXS valves, the RFL relieves compressor pressure surge caused by changing gears or backing off the throttle and has been used on turbo charged engines running upto 35 psi boost. This blow off valve comes everything needed to complete the installation.