Pipe caps: domed steel weld on 4" OD (Pipe Caps of Texas) | eBay
Amazon.com: 4" Inch Metal Tee Cap - Round Vent Cover - Galvanized Steel - Indoor and Outdoor Pipe Cover - Dryer Vent Cover - Dryer Duct End Cap - 4In Metal End
Pipe Fittings Direct. 4 inch schedule 40 SA-234 carbon steel weld on caps
Amazon.com: Vent Systems 4" Metal Tee Cap with Handle. Galvanized Steel End Cap. Dryer Vent Cover. Dryer Duct End Cap. 4In Steel End Cap. Steel Plug 4 Inch. Round Metal Duct Fitting. :