Last on our installation list is the duct work. The Gen-IV evaporator case uses two different outlet sizes, a 2-inch-diameter for the defroster vents and a 2 1/2-inch-diameter for the main dash outlets. Be certain you're using the proper size duct for the vent you are routing and ensure the duct is not in the way of any moving object, like the glovebox, ashtray, wiper mechanism, and so on, and then cut the duct to length. You want a small amount of slack/flex in the duct, so don't make the routing too tight. At this point, it's simply a matter of routing your heater hoses and having the system charged by a professional shop and you're done.