... Duct has many advantages such as fireproof, moisture-resistance, high strength and light,anti-deformation, non-toxic,heat insulation, sound insulation ... density about 0.9g/cm3-1.2g/cm32. Flexible and easy to make proper sculpt and designs3. ... life4. Antisepsis mmothproof ,ant proof5. Heat preservation ,heat insulation ,sound insulation6. scientific prescrption ,real green and environmental material7 ...