Speedi-Products EX-TDK 425 4-Inch Diameter by 5-Feet Length UL Transition Duct Kit with Spring Clamps Speedi-Exhaust Products are made in the USA Used in non insulated general purpose venting systems Multi-ply metalized polyester and aluminum polyester laminate with steel wire support Seal joints with approved duct mastic sealants and tapes Consult your local building codes for approved installation practices