Attic Roof Ventilator Base Compatible Grainger Part Number 2C531 Finish Galvanized Flashing Size 20 in x 20 in For Fan Type Wind-Driven Turbines Includes 20 in x 20 in Flashing Material Galvanized Steel Throat Diameter 12 in Base Type Adjustable Roof Pitch Range 0 12 to 7 12 Base Width 20 in For Use With 12 in Turbine Ventilators Outlet Diameter 12 in Overall Height 7 in