duct 6" adapter for aprilaire 500 600 400 furnace humidifier

this goes on the outlet because they dont wanna make it easy and let a 6 inch duct slip in . they made it 6 1/4" so this adapter is needed for a common 6"id duct....this duct runs back to the blower bottom chamber of ur furnace to put the himidified air into heater ducts throughout house :)