This Broan Wall Vent Ducting Kit Is The Perfect Easy-To-Install Vent For A Kitchen Or Bath Ventilation Fan. It Will Work With 3" Or 4 In. Ductwork And Includes A 3 In. To 4 In. Adapter For Convenience. The Kit Comes With All Parts Need For Installation, Including 5 Ft. Of 4 In. Diameter Flexible Foil Ducting, 4 In. Metal Duct Connector, 3-4 In. Duct Adapter, 2 Nylon Zip Ties And 4 Mounting Screws. The Flexible Ducting Conforms To Ul 181 Class 1 Air Connector Requirements.