- Flexible, female sleeve element to combine male flat duct elements- Directly integrated sealings for full airtightness without necessity for any duct-tapes. Aerodynamically optimised design to minimise pressure loss and maximise air flow rate. Easy-to-connect via time saving click mechanism.- This accessory complies with the Needle Flame Test (according to IEC 60695-5-11), the V2 flammability class (according to UL94) and the B1 building material class (DIN 4102-1)