Gray Flex's models 4GF(R-4.2),4GF-6(R-6.0),and 4GF-8(R-8.0) are tested in accordance with U.L.181 and approved for use as a Class 1 air duct material.
R-Values are determined in accordance with ADC Flexible Duct Performance & Installation Standards as published in 1991 per ASTMC-518 at installed wall thickness in flat configuration.
Fire Safety Rating: UL-181 (Flame spread less than 25, smoke less than 50
Maximum velocity: 5500 FPM
Maximum Operating Temperatures: -20F to 250F
The airtight core is our exclusive patented, reinforced inner liner. Fiberglass insulation is a minimum of 1 1/4" thick for 4GF, min. of 2" for 4GF-6, and min. of 2 5/8" for 4GF-8. The R8 Flex Duct Bag is part of the Snaprite line.