Hart & Cooley F216 12x25 (51330) R6.0 Metalized Jacket Insulated Flexible Air Duct with 2-Ply Black Polyester Core - 12" x 25' 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) R6.0 UL Listed