A 200mm twin wall to flex adaptor is a item used to connect a twin wall flue pipe system to a flexible flue liner. The adaptor has a screw fix coupling that screw onto the flexible flue liner. It's essential for transitioning between these two types of flue systems, allowing you to use a twin wall system within an existing chimney or connect a flexible liner to a twin wall setup.
This transition must be made inside an existing class 1 Chimney. (no flex should be visible outside the brick or clay chimney.