For ventilation duct connection, flexbile ducts are widely used in HVAC duct system. There are different flexible ducts:
.Aluminum foil with steel wire reinforced
.Metallized PET film with steel wire reinforced
.Pure aluminum
.Aluminum foil + PVC + steel wire reinforced
.Aluminum foil + fiberglass cloth + steel wire
.PVC + steel wire
.Fire and water proof cloth with steel str