The Semi-rigid aluminum flexible ducting manufactured from pure aluminum corrugated strips, spirally wound, to produce a double over-lapped joint to prevent uncoiling in use. Semi rigid aluminum ducts are used in heating, ventilation and air-conditioning systems, to connect air outlets to the duct work. If you are interesting this flexible duct machine, Pls feel to contact with us, jv@jack-aiva.com / whatsapp +86 13915206868