The NSI GZ-1 Die Cast Zinc Ground Clamp grips on conduit between 1/2" to 1" in diameter and makes running ground conductor easy. The die cast zinc clamp body and zinc-plated steel screws are made of corrosion resistant, high-quality metals that provide durable performance in a range of applications. Use this clamp to connect bare copper wiring for grounding in indoor environments. cULus Listed 467 for Grounding and Bonding. Stock products you can rely on—stock NSI.