The new flue system is easy to install with push-fit connections and a telescopic system which, in most cases, eliminates the need to cut the flue to size. The Vaillant Telescopic Horiontal flue is a versitile adjustable length flue designed to expel exhaust gases horizontally through an exterior wall. Complete with a 90 degree elbow for connecting the flue to the top of the boiler. Telescopic adjustable length: 498-713mm