Flexible Insulated Ducting Consists of a flexible helix core made of 2-ply polyester laminate and corrosion-resistant zinc-coated wire, surrounded by a blanket of glass fiber insulation, jacketed by a heavy-duty, fire-retardant black polyethylene vapor barrier. Can be installed in place of galvanized pipe in most applications. Due to its flexible nature, the need for elbows is eliminated, allowing for ease of installation in difficult to reach areas. It cuts easily with a knife and snips. The insulation blanket and vapor barrier jacket help reduce heat loss and condensation build-up. Applications include heating, air conditioning, exhausting, dryer venting, and fresh air intakes. Temperature range 20 deg. F. Velocity 6000 FPM feet per minute . C value 23 min. UL Underwriters Laboratories and ULC Underwriters Laboratories of Canada approved as a Class 1 air duct. R4.2 insulation. Please check local codes for permitted uses. Temperature Range 20 F, Inside Diameter 4 , Length 25', Velocity 6000 FPM, C-Value 23 min, Grade UL and ULC