4" Double Duct Adapter. 4" DOUBLE DUCT ADAPTER FOR 4C448 465 cfm DAYTON BLOWERS connect 4 inch ducting to fan or wall.This fan tube adapter will mount to the exhaust port of the Dayton 465 cfm and 750 cfm blowers. You can attatch this fan tube adapter to the wall for intake air and run plastic 4 inch ducting to a box that contains the blower. Attach the fan tube adapter or adpters to the box. Fasten anoth... — Ships from Portland, Oregon USA....more info.