VENTS 4 in. KOM 100 U round back valve is especially designed to prevent back-draft. The spring loaded back-draft damper is manufactured of galvanized steel and contains rubber seal. Easily fits into your vent system， the installation requires minimal labor and time.
Prevents outside air from penetrating the home
Rubber gasket in closed position ensures minimal leakage
Well-balanced
Inserts into duct for simple installation
Fits into 4 in. round ducting
Horizontal installation only
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