Quietflex 5" R6.0 Metalized Insulated Flex Duct - 25' Box Class 1 Air Duct Boxed 25 foot length Metalized polyester jacket reinforced with fiberglass scrim Two-ply black polyester core with encapsulated wire helix Formaldehyde-Free insulation is substantially less irritating than traditional insulation Greenguard for Children and Schools Certified Greenguard Highly Microbial Resistant rated (Level 4) R4.2 UL Listed