Maximize the air and sound performance of your Broan ventilation fan or range hood using one of our wide variety of ducting accessories.Footprint is 18-3/4 in long x 14-1/4 in wide for a well-balanced fitDesigned to fit with 3-1/4 in x 10 in or up to 8 in round duct for flexible installationA built-in, backdraft damper and bird screen provide a dependable roof cap you can count onRoof cap is made of 24 ga CRCQ steel construction with a black electrically-bonded epoxy finish for durability and long life