Continental Fan Manufacturing BDD175 Exhaust Fan N A Accessory Backdraft Damper Gravity Operated Backdraft Damper for 7" DuctingDampers function as flow regulators and prevent ventilation when not desired such as when the system is not in use Let us provide all the accessories needed to install an AXC In Line Duct Fan or EXT External Mount Exhaust Fan Continental Fan Company was established in 1986 to manufacture and distribute quality ventilation equipment Their objectives then were simpleÂ... to provide superior products dependable service and competitive pricing They remain unchanged today Features:Low air leakage designGalvanized steel housingAluminum butterfly damper bladesGravity operated closureInstall in horizontal or vertical (upblast only) positionIdeal for supply or exhaust applicationsFits 7" Round ducting