POWERTEC 70104 4-Inch to 2-1/2-Inch Reducer Connect 4-Inch opening to a 2-1/2-Inch hose or a 2-1/2-Inch opening to a 4-Inch hose Adaptable to Shop-Vac, Sears and a variety of other wet/dry vacuum cleaning Tough, durable ABS plastic material 2-1/2-Inch nominal end measures 2-31/64-Inch O.D. and 2-19/64-Inch 4-Inch nominal end measures 3-15/16-Inch O.D. and 3-45/64-Inch I.D.