Sigma Electric ProConnex 41309 Ground Clamp 1/2 to 1-Inch, 1-Pack Connects bare wire to copper or steel water pipe or tubing For pipe or copper rod sizes 1/2-in thru 1-in, wire range #10 - #2, and rebar range 5/8-in thru 3/4-in Copper alloy construction with zinc-plated steel screws Product is UL and CSA listed