Silverduct UL 2158A clothes dryer transition duct provides flame resistance. It crushes easily behind the dryer and is held together with layers of aluminum foil and polyester plastic. Clothes dryer manufacturers may limit the use of plastics in venting. Check the dryer warranty and installation instructions as well as your local building codes for appropriate use.Non-insulated, non-combustible flexible aluminum air ductAluminum roll formed with crimp-locked seam4 in Dia aluminum semi-rigid ductClass 0 duct