Heavy Duty Bronze Ground Clamp with Wire Adapters for 2.5-4 in. Pipe Heavy Duty Bronze Adapters have serrations that match the serrations on the ground clamp, assuring positive lock. All adapters fit all clamps for the ultimate in flexibility. Zinc plated steel hardware. Used to connect grounding conductor to rigid conduit on water pipe. UL Listed 467 Grounding and Bonding.