The Circular Flange System (BCT) is providing a higher stability to the circular ducting networks, thanks to rigid connections of the ducts. This system reduces installation and assembly costs. The BCT is composed by a central connection piece and 2 circular flanges. It is tested in accordance with HVAC air leakage test procedures for Ductwork Jointings Systems DW/TM1 witnessed by BSRIA. All dimensions between 200-2000 mm are suitable for pressure classes A, B and C.