The Ultra Breeze Vent Cover from Fan-Tastic Vent has revolutionized the design of vent protection devices. Not only does it allow you to keep your vents open in the rain, but the exclusive patent pending airfoil technology allows for up 75% more airflow than competing products. The Ultra Breeze has been field tested to provide superior protection for your vents, while allowing between 95-100% airflow - The highest of any vent cover on the market! Tested to limit virtually no airflow, while the finer mesh screens typically found in other covers can cut down airflow significantly.