Non-insulated flexible air duct. Constructed with spring steel wire helix, encapsulated in 2-ply, air tight inner core. Maximum Positive pressure; 6"W.G. (4"-12") 4" W.G. (14"-20") Maximum Negative pressure; 1" W.G. (4"-10") 1/2" W.G. (12"-20") Maximum Velocity; 4,000 FPM Operating Temperature: 0-200 F 3/8" oversized inner core/tinted adhesive for darker appearance. Excellent Flexible air duct for low to medium-pressure environmental remediation applications. Engineered and designed for use with negative Air Machines, scrubbers and other remediation/abatement equipment. The BLK-NI is constructed from two layers of polyester film. Both layers are clear polyester, no coatings.