NuTone Roof Cap, Steel, Black, Baked Enamel, Suitable for: 3 or 4 in Round Duct, Includes: Bird Screen, DamperRoof cap fits three or four in round duct for versatilityBuilt-in backdraft damper and bird screen are standard and a bonus that adds to your confidenceSteel baked black enamel finish for durability and long life that stands up to the elementsDo not use for dryer venting