Builder's Best GRV624 Series - 4" Diameter Galv. Roof Vent Hood with Flapper and Screen is made from 26-gauge galvanized mill finish steel for lasting strength and durability. The flush tail design ensures a neat, streamlined installation, while the built-in flapper supports efficient airflow and reduces backdraft. A 1/4" x 1/4" removable screen helps block debris and pests.