<p>The Revitalizaire backdraft damper contains a double-lipped EPDM rubber seal on both ends which allows for easy install without the use of sealants or solvents. With a diameter of 3 7/8th inches, the damper will interface with 4 inch ducts with little hassle. Once installed the damper can be twisted and adjusted without compromising the seal.</p> <p>The 0.5mm spring-loaded design allows the unit to be installed in any orientation without compromising its ability to close</p> <p>Strict quality control ensures no air gaps. The durable galvanized steel design allows the unit to function in any climate.</p>