Crayflex is a very strong fully flexible compressible light weight duct which is widely used in Air Conditioning and Ventilation Systems for Commercial, Industrial and Residential applications. Crayflex is extremely durable and will maintain dimensional stability when fully extended. Highly efficient when correctly installed, Crayflex provides a maintenance free service life under normal operating conditions. All Thermal performance (R Value) are classified by Underwriters Laboratories (UL) in accordance with Air Duct Council (ADC) flexible duct performance.