Attic Roof Ventilator Base Compatible Grainger Part Number 2C533 Compatible Manufacturer Model Number TV16G Finish Galvanized Flashing Size 20 in x 20 in For Fan Type Wind-Driven Turbines Material Galvanized Steel Throat Diameter 16 in Base Type Flat Base Width 26 in For Use With Flat Roof Mounting Base 16 in Galvanized Outlet Diameter 16 in Overall Height 10 in