Charlotte Pipe 6 in. x 8 in. DWV PVC Pipe Increaser Reducer Bush PVC 00102 1900 - The Home Depot
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