Attic Roof Ventilator Base Compatible Grainger Part Number 4C016 Compatible Manufacturer Model Number TV04G Finish Galvanized Flashing Size 20 in x 20 in For Fan Type Wind-Driven Turbines Material Galvanized Steel Throat Diameter 4 in Base Type Flat Base Width 14 in For Use With Flat Roof Mounting Base 4 in Galvanized Outlet Diameter 4 in Overall Height 10 in