The application of aluminum PET foil products in flexible duct mainly focuses on heat insulation, water vapor barrier and enhancing the physical properties of the duct. Heat insulation performance: Aluminum PET foil products have good heat insulation performance because of their unique material combination. In the flexible duct, aluminum PET foil products can be used as an insulation layer to effectively isolate the external heat source, prevent heat from entering the duct, ensure the stability of the air temperature in the tube, so as to save energy and improve the system efficiency. Water vapor barrier: aluminum PET foil products also have excellent water vapor barrier performance. In the flexible duct, the penetration of water vapor may cause moisture inside the duct, which may affect the air quality and service life. Aluminum PET foil products can effectively prevent the infiltration of water vapor, keep the dry inside of the air duct, and prevent the condensation and corrosion phenomenon. Enhanced physical properties: aluminum PET foil products have high strength, tear resistance and wear resistance. These characteristics make the flexible air duct not easy to be damaged when subjected to external pressure or friction, and improve the durability and service life of the air duct. At the same time, the addition of aluminum PET foil products can also enhance the rigidity and stability of the duct, so that it can maintain good shape and function in a complex environment.