Duct Inline Reducer Increaser Connector to Vent Adapter 3 4 5 6 Inch // 80-150 mm - - Amazon.com
6 Inch to 4 Inch HVAC Duct Reducer & Increaser - Galvanized Sheet Metal Ducting Connector for Airflow, Heating, Cooling, & Air Ventilation System Extra Strength and Fittings - Ducting Components - Amazon.com
GE RAK6053 Duct Adapter for GE PTACs
AC INFINITY Duct Reducer, 8-Inch to 6-Inch Adapter Cone, Galvanized Steel - AC Infinity
AC INFINITY Duct Reducer, 8-Inch to 6-Inch Adapter Cone, Galvanized Steel - AC Infinity