Amazon.com: 4" to 3" OR 3" to 4" Round Metal Pipe Reducer OR Increaser - Galvanized Steel Construction : Tools & Home Improvement
1" 4-Way Side Outlet Tee, Home TZH Malleable iron Pipe Fittings for Industrial vintage style, Flanges with Threaded Hole for DIY Project/Furniture/Shelving Decoration (10, 1") - Amazon.com
HVAC Premium Round Metal Pipe Reducer & Increaser | 8" to 7" HVAC Duct