This model is a rear flanged general purpose exhaust shutter. The blades have a galvanized steel reinforcement strip across the top of each blade for added strength and counter balancing efficiency. The blades have a felt seal on the leading edge for quiet closing and better protection from the weather. Ideal for use with direct-drive or belt-driven exhaust fans. Item: Backdraft Damper / Wall Shutter Fits Fan Dia.: 30" Shutter Overall Size: 33" x 33" Shutter Construction Material: G-90 Galvanized Steel Frame and Tie Rods Shutter Opening Required: 30-1/2" x 30-1/2" Shutter Free Area: 5.452 sq. ft. Shutter Mounting Position: Vertical Shutter Mounting Location: Wall Shutter Item: Backdraft Damper / Wall Shutter Frame Depth: 3" Open Depth: 6-1/4" Flange Width: 1-1/2" Mounting Hole Size: Prepunched Max. Velocity: 2500 FPM Blade Material: Mill Finish Aluminum For Use With: Vertical Mounted Exhaust Fans Number of Panels: 1