This 150mm round PVC joiner incorporates a gravity-operated backdraft flap to provide a straight connection and one-way airflow control in a single fitting. The flap opens when the fan is operating and closes when airflow stops, helping restrict outside air, odours and insects from entering through an exhaust duct. Manufactured from lightweight, corrosion-resistant PVC, the fitting connects directly to compatible 150mm round duct and is particularly useful for bathroom, laundry and kitchen extraction systems exhausting to the exterior.