Drain Coupling, 5 to 4 in. Straight Adaptor, PVC Rubber
Vent Systems 4" to 5" Inch Duct Reducer Adapter Connector Fitting Pipe Increaser Reducer Cone for HVAC Ventilation Systems, ABS Plastic PVC Pipe 125 to 100 mm - Amazon.com
Formufit 1-1/4 in. Furniture Grade PVC 5-Way Cross in White (4-Pack) F1145WC-WH-4 - The Home Depot