Backdraft Damper / Wall Shutter Fits Fan Dia 36 in Shutter Overall Size 39 in x 39 in Shutter Construction Material G-90 Galvanized Steel Frame and Tie Rods Shutter Opening Required 36-1/2 in x 36-1/2 in Shutter Free Area 7.436 sq ft Vertical Shutter Mounting Position Shutter Mounting Location Wall Frame Depth 3 in Open Depth 6 1/4 in Flange Width 1 1/2 in Mounting Hole Size Prepunched Max Velocity 2500 FPM Blade Material Mill Finish Aluminum