8" x 6" PVC Duct Rolled Reducer Coupling, 1034-RCR-0806
Charlotte Pipe 6 in. x 8 in. DWV PVC Pipe Increaser Reducer Bush PVC 00102 1900 - The Home Depot
Zoro Select PVC Reducer Bushing, Spigot, 8 in x 6 in Pipe Size 837-585 | Zoro
Vent Systems 8" to 6" Inch Duct Reducer Adapter Connector Fitting Pipe Increaser Reducer Cone for HVAC Ventilation Systems, ABS Plastic PVC Pipe 200 to 150 mm - Amazon.com