Dayton 36 in 38. 75H-W 4. 5L Alu Intake Shutter Dampr, 37 in x 37 in . . . Key Features Shutter Mounting Position Vertical Shutter Mounting Location Wall Shutter Construction Material Extruded Aluminum Frame and G-90 Galvanized Tie Rods Shutter Free Area 6 629 sq ft Shutter Opening Required 37 in x 37 in