Dual outlet-type BOV. Dual Port vents both to the atmosphere and back into the air intake. Ports with sequential timing allow quieter operation during everyday driving while getting all the benefits of a vent-to-atmosphere BOV under race conditions. They are easily converted to a complete atmospheric or whole bypass unit using supplied port blanking plug.
 
Please note;
 
When using this with a TTS Rotrex super charger kit please order the 25mm 4-5mm reducer option
 
 that twin-turbo applications, such as the Audi S4 2.7L (B5) 97-01, will require two valves.