TDC (Transverse Duct Connector) system is a separate flange install onto the for rectangular ductwork. The flanges attach to the duct wall and have an integral mastic which allows the flange to seal itself to the duct. Octopus Metal offers wide range of TDC flanges at very competitive price through a complete supply chain. Material: Galvanized Steel, Stainless Steel 2) Available in zinc coating: 80g/m² - 275 g/m² (G25 - G90) 3) Specifications: Item No. Size Thickness OCT-F20-A 20mm 0.8mm OCT-F30-A 30mm 1.0mm OCT-F40-A 40mm 1.2mm Assorted duct corners are available. Standard export packing.