Attic Roof Ventilator Base Compatible Grainger Part Number 2C802 Compatible Manufacturer Model Number TV20G Finish Galvanized Flashing Size 20 in x 20 in For Fan Type Wind-Driven Turbines Material Galvanized Steel Throat Diameter 20 in Base Type Flat Base Width 32 in For Use With Flat Roof Mounting Base 20 in Galvanized Outlet Diameter 20 in Overall Height 10 in