Ideal Vacuum | Buttweld Concentric Reducer 4.0 to 2.5 Inch OD, weld-on, Stainless Steel, PN: A2505001B004025
2" x 1" NPT 304 Stainless Steel Reducer Coupling, Class 150
Amazon.com: 8SC82 Exhaust Pipe Reducer Component Adapter 2.5 Inch OD to 3 Inch OD 4 Inch Length Polished 304 Stainless Steel Universal 2.5"OD to 3"OD Exhaust Pipe Reducer Adapter-2PCS : Automotive
T-304 Stainless Steel Pool Concentric Reducer - 3 inch outlet - 6 inch inlet