4 inch roof vent with backdraft damper still have an airflow of UP TO 75 percent . High-quality galvanized steel to durability and long-lasting use. The high-performance polyester powder coating has strong resistance and excellent protection. The roof vent 4 inch comes with a 120mm x 90mm mesh cover, with a grid space of about 3mm to effectively prevent the entry of small animals or birds. roof dryer vent is designed for maximum airflow and protection, to be used with kitchen and roof exhaust venting systems, can be used in conjunction with 4 inch duct and exhaust fans for house ventilation. 4 inch vent includes a pipe extension located underneath the flange for connecting to flex ducting, and there are four holes in the panel, which can help you install on the 4inch bathroom exhaust fan roof jack more firmly. Colour:Black Material:steel Package Contents: 1 x Roof Vent Cap Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is 1-3cm.