A connector to connect a chimney liner with a flexible stalflex duct. Wall-mounted chimney liners are made of acid-resistant chromium-nickel steel sheets, grade 1.4404 according to DIN 17441, thickness 0.5 to 0.8 [mm]. They are mainly used to remove flue gases from gas or heating oil-fired heating devices operating under vacuum. Such chimneys are resistant to the corrosive effects of acid condensate formed during the combustion process. Water vapor condenses on the cool internal walls of the chimney and is discharged in the form of condensate through a condensate pan at the bottom of the chimney. Condensation may occur during the start-up or cyclical operation of the boiler.