PANASONIC Duct Adaptor: Metal - 32NA44|FV-VS43R - Grainger
Abs Duct Fan Connector Wall Range Hood Flange Adapter Kitchen Air Vent Exhaust Hood 100/120/150/200mm For Ventilation System - Pipe Fittings - AliExpress
8 X 5 Vent Pipe Reducer - HVAC Ductwork Sheet Metal - Indoor Comfort Supply
Everbilt 4 in. Round to Oval Dryer Duct Adapter R2OHD - The Home Depot
GE RAK6053 Duct Adapter for GE PTACs
LB White Duct Adapter | QC Supply
WhisperValue® DC™ 24 Gauge, fire code rated, 4" oval to 3' round | Crescent Electric Supply Company