flue duct starter element between the heating appliance and the flue system. Designed for installation on the heating unit's outlet pipe to transition from a "smoke" flue system to a "condensate" system. The internal contour is made of 0.8 mm thick AISI 430 stainless steel. No thermal insulation. Cold-formed socket joint with ideal geometry and gas tightness. Laser butt welding ensures a thin and durable seam, significantly increasing service life. Operating temperature up to 600°C.