Combining the functionality of a joiner with the benefits of a backdraft damper, this Airmiq component ensures one-way airflow within a ducted system. A gravity-operated flap inside the fitting closes when the fan is off, preventing external air, insects, or odours from entering the building. Particularly useful for systems exhausting to the outdoors, such as bathroom fans or kitchen extraction, it helps maintain indoor air quality while simplifying installation by combining two components into one.