Santa Fe Dehumidifier 10" Flex Insulated Duct 25' (4022126) is an optional add-on to these dehumidifiers: Advance2, Force, Impact XT, Max Dry Dual XT. Duct work is useful if you need to hide the dehumidifier, need to dehumidify an otherwise inaccessible area or pump air from one room to another. This duct is 25 feet long and 10 inches in diameter which will allow you to use in different areas or keep it hidden. It is very flexible to accommodate most situations. This flex duct is just one part of the total materials that you need to properly duct the dehumidifiers. A register head(s), ducting collar(s), and register grills(s) in 10'' is needed. To attach the duct to the dehumidifier, you need a duct kit of the same size, which is sold separately. This flex duct is perfect for ducting the 2 supply (Outlet) vents for the above dehumidifiers. 12'' flex duct is used for the Return (Inlet) vent and is sold separately. The insulation of the duct keeps the dehumidifier more energy efficient.