Santa Fe Dehumidifier 12" Flex Duct 25' (4024750) is an optional add-on to these dehumidifiers: Max Dry Dual XT and Impact 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 for using with the air Return (Inlet) vent and is 25 foot long with diameter of 12 inches. You would use the 10'' flex duct for ducting the 2 Supply (Outlets) vents and is sold separately. This duct is flexible, long lasting and made out of durable material so it can be used in many situations.