Focus Tool has been designed to fit the three main bolts on a standard C-clamp (newer and older) used on par and leko lights. The tool is manufactured out of aluminum so that the focuser can have the tool comfortably hanging from his or her wrist as they work on the lighting fixture but the aluminum is hard coat annodized to make the surface wear resistant. Because it is made out of aluminum, it will not damage steel or iron nuts and bolts. Be sure that the tool is properly seated prior to use. Never use this tool on live circuits.