4" Insulated Aluminum Flexible HVAC Duct R-8.0 – 25' Length Fixed Blades with Damper Complies with industry standards of

Complies with industry standards of USA: ASTM D-882

Looks like it was just waxed

Conveniently taped together as a single piece

scratch-resistant

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4" Insulated Aluminum Flexible HVAC Duct R-8.0 – 25' Length Fixed Blades with Damper Complies with industry standards of+ Product Details High Quality Aluminum housing on the outside and on the inside for the best insulation value Insulation A thick blanket of fiberglass insulation provides you with an R Value of 8. 0 Energy Efficient Air tight inner core decreases the pressure loss and provides a more hygienic environment high energy efficient No fiberglass erosion into air stream Design Designed to withstand bends and sharp turns without kinking. Tough reinforced