Type FLEXTRO flexible plenum boxes for the connection of circular and square diffuser faces to circular ducts, suitable for supply air or extract air applications in comfort and industrial zones, Damper blade for volume flow rate balancing, can be set in 15° intervals between 0 and 90°, Equalising element that ensures the best possible airflow through the diffuser face (supply air), Metal angled support rod, with interlock, to erect the plenum box