THE ALUMINUM WALL SHUTTER IS A REAR FLANGED EXHAUST SHUTTER FOR AREAS WHERE CORROSION MAY BE A PROBLEM. THE FRAME AND BLADES ARE MILL FINISH ALUMINUM. THE BLADES HAVE A GALVANIZED 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. RECOMMENDED FOR VERTICAL MOUNT EXHAUST APPLICATIONS ONLY. MADE IN THE USA