The Hybrid valve is back! In 1999, GFB's first Hybrid valve pioneered the dual port design, which was so successful the technology has since been adopted by most other brands. By "staging" the two venting outlets, at low valve lifts most of the air is recirculated. As the car is driven harder, the valve opens further and more of the atmosphere venting port is exposed for a louder sound the Hybrid is a dual outlet valve for combined recirc and atmosphere venting, this system makes it possible to be used on cars with sensitive airflow meters. Universal 20mm inlet, 20mm outlet