BOV boost pressure relief valve AMAZING SOUND EFFECT !!! Protects your turbo !!! The standard DV valve forces the air into the circulation, while the Blow Off valve - the atmospheric valve lets the air out, which protects your turbo, and at the same time produces an amazing sound effect - characteristic PSSSSSTT !!!! Dedicated to: Subaru 2002 - 2007 Impreza WRX / STI High quality. Valve - 6061 aluminum, CNC machined Dimensions: Inner diameter of the inlet (piston): 27mm. Bolt spacing: 105mm. Boost pressure relief valve BOV AMAZING SOUND EFFECT !!! Protects your turbo !!! DV valve forces the air into the circulation, while the Blow Off valve - the atmospheric valve lets the air out, which protects your turbo, and at the same time produces an amazing sound effect - characteristic PSSSSSTT !!!! Dedicated to: Subaru 2002 - 2007 Impreza WRX / STI workmanship.Valve - Aluminum 6061, CNC machined Dimensions: Inner diameter of the inlet (piston): 27mm. Bolt spacing: 105mm.