BACKDRAFT DAMPERS ARE NON-FLANGED HORIZONTAL MOUNT EXHAUST BACKDRAFT DAMPER. THE FRAME IS GALVANIZED STEEL WITH ALUMINUM BLADES. THE BLADES HAVE A FELT SEAL ON THE LEADING EDGE FOR QUIET CLOSING AND BETTER PROTECTION FROM THE WEATHER. SPRING ASSISTED TO ALLOW THE BLADES TO OPEN QUICKLY. IDEAL FOR USE IN ROOF CURBS, DUCTWORK, OR WALL COLLARS WHEN USING A FAN OR POWER ROOF VENTILATOR. RECOMMENDED FOR HORIZONTAL MOUNT EXHAUST APPLICATIONS.