Simple to install, the kit is comprised of push-fit connections and positive screw fixings. The kit contains a horizontal air duct, flue corner, 60mm air duct clamp, 30mm air duct clamp, internal trim ring and external wall seal. Suitable for the Vaillant ErP boiler ranges. This current model is a direct replacement to the old Vaillant Horizontal Flue Kit model 303933. Vaillant Ecotec Plus Regular (open Vented).Vaillant Ecotec Plus System Boilers.