The Type H Blow Off Valve(BOV) features a linear rate spring design which ensures valve fully opens once actuated for excellent response. A 360 degree vent surface allows for increased piston support without sacrificing flow. It reaches 110 db @ 10PSI!!! The Type H Kit includes : TurboXS Blow Off Valve Type H Mild Steel Zinc Plated Weld-on Adaptor Aluminum Weld-on Adaptor Spring Adjusting Packer Washers For custom turbo applications, the TurboXS Blow Off Valve Type H is installed directly into the connecting pipe running between the turbo and the throttle body housing. MUST PURCHASE WRX, EVO, or SRT-4 ADAPTOR KIT TO INSTALL BOV WITHOUT MODIFICATION!!!!