Woodstock W1044 4-to-2-1/2-Inch Reducer 4-Inch and 2-1/2-inch Outside Diameter 4-Inch end connects to standard 4-inch dust collection hose 2-1/2-Inch end connects directly to shop vacuum hose ABS Plastic Use optional model D4620 Double-Sided Quick Connect with 4" Tapered ID for direct connect to 4" dust ports and fittings