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. Atco Flexible Air Duct, Insulated, Series: 030 Series, 12 in Inside Dia, 25 ft Length, 5000 fpm, R4.2 Insulation Value, 0.05 perm Vapor Transmission, -1 to 6 in-WG, -20 to 140 deg F, For Use With: Complete Air Duct System and/or a Branch Duct Connecting to Mixing Boxes, Diffusers, Light Troffers, Room Inlets or other Terminal Devices, Polyester/Fiberglass/Metalized Polyester, Silver, Domestic