These trick new flapper valves are installed in the back side of the air box on 2006-09 Polaris 600/700/800 H.O. IQ and IQ RMK models to provide additional air flow to the engine. They are activated by air box vacuum. When the stock intake begins to plug in deep powder snow conditions these valves open to deliver the necessary air flow that the engine demands. This substantially improves consistency when running in deep powder snow conditions. Sold per pair. (Not for Race Chassis)