Santa Fe Dehumidifier 12" Flex Insulated Duct 25' (4028366) is an add-on to these dehumidifiers: Max Dry Dual XT and Impact XT. Ductwork is useful if you need to hide the dehumidifier, need to dehumidify an otherwise inaccessible area or pump air from one room to another. To attach the duct to the dehumidifer, you need a duct kit of the same size, which is sold separately. The insulation of the duct keeps the dehumidifier more energy efficient.