Trident Polyduct – The most flexible, crush proof and rugged blower duct hose for Heat, Ventilation and Air Conditioning* (HVAC). Heavy Duty polypropylene hose, reinforced with a flexible polypropylene rod helix. It has excellent flexibility & compressibility; and excellent resistance to crushing, flex fatigue, tearing, and moisture*. Stomp on it and it returns to shape without damage. Shove it thru tight openings and overheads and it delivers full air flow. Meets FMVSS 302 flame resistance, Temp. Range: -40°F to +225°F (-40°C to 107°C). *when insulated