Broan's 459 round transition can maximize the air and sound performance of your ventilation fan or range hood. It's compatible with most 3-1/4 in. x 14 in. rectangular and 8 in. round ducts and connects a 3-1/4 in. x 14 in. rectangular duct to an 8 in. round duct. The 30-gauge galvanized steel construction provides longevity.