AIR VENT RVG51000 Galvanized Vent, Mill, 50 SQIN Net Free Area, 16-3/4" x 18-3/4" Base, 9-1/2" Diameter Opening, 8" x 8" Aluminum Screen, Square Dome, Louvered On 3 Sides, Fits Types, Good for 3/12 to 10/12 Roof Pitch