Steel Clamps for attaching ducting to fans, filters, reflectors, and whatever else needs clamping! Strong metal construction - you need a screw driver or a wrench to adjust. Count on a secure fit with this four-inch metal Flex Duct Clamp. The worm drive-style allows for easy adjustments of the heavy-duty mechanism so you can loosen or tighten the clamp with a simple twist of a screwdriver.