Introducing the Dust Collection 4 to 3 Inch Reducer by POWERTEC. This dust collection fitting allows you to connect a 3" ID opening to 4" flexible hose and/or transition a 3" ID opening to 4" ID standard hose. It's easy to use and offers a secure, quick attachment to your dust collector hose. It's ideal for increasing air velocity near the machine where it's needed most. Additionally, it features a tapered port on one side that fits inside most 3" dust collection hose. We make our reducers utilizing premium ABS plastic material, which provides long-term durability with resistance to rust and corrosion. It's thick walls are intended to stand up to hose clamp pressure and the abrasive nature of woodworking and workshop dust collection. /Specifications/. Color: Black. Material: ABS Plastic ?4-Inch Nominal End Measures: 3-61/64-inch outer diameter by 3-59/64-inch inner diameter 3-Inch Nominal End Measures: 2-63/64-inch outer diameter by 2-23/32-inch inner diameter.