Thermaflex® G-KM Flexible Duct

Flexible Air Duct

Highly efficient, thermally insulated flexible duct for use in low and medium pressure heating and cooling systems. Acoustically rated, self-extinguishing CPE core easily expands over fittings. Core is permanently bonded to a coated spring steel wire helix that supports an ample blanket of fiberglass insulation over a fiberglass scrim and a tough polyethylene vapor barrier. Smooth liner, insulation, and tough vapor barrier provide even airflow and a double air seal.


  • Acoustically rated, self-extinguishing CPE core
  • Easily expands over fittings
  • Even airflow

G-KM Specs

Diameter 3-20 inches ID
Pressure Rating (WG)
Positive 6 inches (3˝-16˝ ID)
4 inches (18˝-20˝ ID)
Negative 1 inch (4˝-12˝ ID)
1/2 inch (14˝-20˝ ID)
Velocity 5000 FPM
Temp. Range -20°F – 200°F cont.
-20°F – 250°F intermittent
R-Value R-4.2, R-8.0
GREENGUARD Certifications GREENGUARD Indoor Air Quality Certified
GREENGUARD Children and Schools Certified


This product can expose you to chemicals including Antimony Trioxide, which is known to the State of California to cause cancer. For more information go to