Just 2 in H for better appearance. Injection-molded, high-impact resin construction for long life. Colors complement most roofs. Pre-drilled nail holes make installation easier. 11-3/4 in x 9-3/4 in opening, 18-1/2 in x 17-1/2 in flashing, 4-1/4 in H, 37 sq-in of net-free ventilating area.