Dundas Jafine BTD48 Proflex Clothes Dryer Transition Duct, 4-Inch, Aluminum Ideal for gas and electric dryer applications Constructed of heavy duty, fire resistant, 4 ply aluminum foil laminate that encapsulates a high density, corrosion resistant wire helix Forms an air tight and easy to use air duct Duct will not support combustion UL2158A labeled and marked