The AK14 is an outside air kit from Hearth & Home Technologies that brings combustion air to select fireplaces from outdoors. The kit includes the door assembly, inlet tube assembly, control arm, wire ties and fasteners. Flexible duct, either insulated ID4 or uninsulated UD4, is not included and is ordered separately. The building-side opening is a 4" hole, and the duct run should be kept as short as possible. Always confirm the fit, approved components and clearances in your fireplace installation manual before ordering. Special order.