Attic Roof Ventilator Base Compatible Grainger Part Number 2C529 Compatible Manufacturer Model Number TV08G Finish Galvanized Flashing Size 20 in x 20 in For Fan Type Wind-Driven Turbines Material Galvanized Steel Throat Diameter 8 in Base Type Flat Base Width 18 in For Use With Flat Roof Mounting Base 8 in Galvanized Outlet Diameter 8 in Overall Height 10 in