Builder's Best ASM320 Series - 4" Diameter Aluminum Standard Mouth Hood with Flapper features a 012 aluminum face and a 010 aluminum tail for lightweight durability. The 11.5" tailpipe is connected with a 360-degree mechanical seam, providing a secure and long-lasting fit. The built-in flapper allows efficient airflow while helping to reduce backdraft, making it suitable for exterior venting applications.