Based on your location it seems like you might be looking for the Canadian site.
Would you like to continue, or switch to the Canadian site?
Ducts, Dampers, Adapters & Caps
Broan-NuTone® Wall Cap, Steel, Black, for 3-Inch and 4-Inch round duct (no bird screen)
Maximize the air and sound performance of your Broan® ventilation fan by using one of our wide variety of termination fittings specifically designed for Broan® fans.