Vent Systems 8" inch Air Vent Duct Connector Flange with Rubber Gasket. Straight Ventilation Pipe Metal Ducting Connector Wall Plate for Cooling Heating Ventilation System HVAC 200mm. - - Amazon.com
4" Inch Couplings for Ducts Without Gaskets - Metal Vent Duct Connector - 4 Inch Vent Extension - Galvanized Metal Pipe Connection - 4 Inch Dryer Vent Coupler (Galvanized Steel, 4") - - Amazon.com