Amazon.com: POWERTEC 70147 4-Inch OD to 2-1/4-Inch OD Hose Reducer Adapter for Dust Collection Systems : Tools & Home Improvement
Cen-Tec Systems 1.25-in x 10ft Conductive Dust Collection Hose with Quick Click Tool Adapters in the Dust Collection Attachments department at Lowes.com
4-1/2" To 3-7/8" Dust Collection Hose Adaptor By Peachtree Woodworking - PW425 - Vacuum And Dust Collector Hoses - Amazon.com
POWERTEC 70345 Dust Collection Reducer Fittings, 4" Hose to 2-1/2" Hose & 4" Port to 2-1/2" Hose, 2-Pc Set - Walmart.com
Amazon.com: POWERTEC 70291-P2 4" Port to 2-1/2" Hose Tapered Adapter Dust Collection Reducer Fitting, 2 PK : Tools & Home Improvement