Maximize the air and sound performance of your Broan ventilation fan or range hood using one of our wide variety of ducting accessories. 4.5-inch x 18.5-inch to 10-inch round vertical discharge transition is made to fit fan and hood outlets that must fit to 10-inch round ducting. Transition is made of 26-gauge galvanized steel construction for durability and long life. Sold as 1 to a carton.