Query: 3 inch backdraft damper
Stovepipe Damper 3"
Labconco 3858800 Backdraft Damper, 3" Height, 10" OD Inlet, 10" OD Outlet
Butterfly Backdraft Damper (3 Inch) (BD 3)
Imperial Mfg Group Usa Imperial Manufacturing Damper 3" Dia. Cast Iron, 1