This trick flapper valve is installed in the back of the air box to provide additional airflow to the engine. It is activated by air box vacuum. When the stock intake begins to plug in deep powder snow conditions, the valve opens to deliver the necessary airflow that the engine demands. This substantially improves throttle response, horsepower and running consistency. Sold as a kit that includes 1 - Powder Valve, 1 - Pre-Filter and hardware for installation.