The RDP Backdraft Butterfly Damper is used as a back draft damper for heat exchangers, exhaust systems, solar heating systems and other intake or exhaust applications where a powered damper is not needed. This damper works in both horizontal or vertical positions (upward airflow only) and the foam seal provides minimal air leakage. Due to its unique design and Aluminum blades, it opens easily with normal air flow and closes with gravity. Quality constructed in Galvanized Steel, gauges 28-22. Rated to -20 to 160 Degrees F.