Broan Roof Vent Kit, 8-Foot Of 4-Inch Flexible Aluminum Duct. Select The Rvk1A Broan-Nutone Roof Vent Kit To Provide Reliable Rooftop Venting. Features A Black Enamel Finish And Is Designed For Use With 3 In. Or 4 In. Round Ducts. Includes A Built-In Back Draft Damper And Bird Screen To Prevent Small Pests From Entering Duct.. This Kit Comes With All Parts Need For Installation, Including 8 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.