Lambro 2841 Worm Gear Clamp, 4 in Duct, Clamping Range: 3-9/16 to 4-1/2 in, Steel

These clamps are made up of zinc-plated steel and are ideal 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.