These clamps are made up of zinc plated steel and are perfect for the installation of most home and industrial dryers. Their unique design allows for easy-to-tighten convenience. Clamps can also be used on most bath fans and other applications. Lambro Worm Gear Clamp, Adjustable, 3-9/16 to 4-1/2 in Capacity, For Use With: Aluminum Duct, Steel, Zinc Plated, Domestic