Additional Details ------------------------------ Product description: Description: Atco #030, 036, and 031 are UL 181, Class 1 Air Ducts and are manufactured with a tri-directional fiberglass scrim reinforced, metallized polyester outer jacket. The inner core of all three products is air-tight and designed for low-to-medium operating pressures in HVAC systems. Atco #036 and 031 have increased insulation for superior thermal performance. Construction: A double lamination of tough polyester which encapsulates a steel wire helix forms the air-tight inner core of the Atco #030, 036, and 031. The double-layer core of each product is wrapped in multiple thicknesses of fiberglass insulation. All three products are sheathed in a rugged and durable tri-directionally reinforced, metallized polyester jacket. Air-tight Inner Core - Energy efficient / No fiberglass erosion into air stream. Encapsulated Wire Helix - No unraveling when cut to length / Quick installation Smooth Inner Core - Low friction loss / Low operating cost. Thick Blanket of Fiberglass Insulation - Energy efficient / Excellent thermal characteristics Tough Reinforced Metallized Polyester Jacket - Tear and puncture resistant / Low maintenance. Lightweight Compact Carton - Reduces warehouse and Jobsite handling cost.