6" X 4" Duct Reducer & Increaser Non-Crimped Single Wall Galvanized Sheet Metal ducting Connector for Airflow, Heating, Cooling, & air Ventilation Systems Fittings - Ducting Components - Amazon.com
Polished 31W Concentric Weld Reducers - 8" x 6" OD (316L)
6” x 4” Stainless Steel Stove Pipe Reducer/increaser 6" to 4" or 4" to 6" | eBay
Pipe Fittings Direct. 6 X 4 inch 304 Stainless Steel tee reducers
6" x 3" Tri Clamp, Tri Clover, Sanitary, Concentric Reducer, 304 Stain – Affordable Distillery Equipment
IMPERIAL 6-in x 4-in Galvanized Steel Duct Reducer in the Duct Transitions & Connectors department at Lowes.com
6-DRATT-4 Dixon Instrumentation Fitting - Stainless Steel Reducer - 3/8" x 1/4" Tube OD (Pack of 10) — HoseWarehouse
Pipe Fittings Direct. 6 X 4 inch 316 Stainless Steel concentric reducers
T-304 Stainless Steel Pool Concentric Reducer - 4 inch outlet - 6 inch inlet