We built the NSI GRC-58H Heavy Duty Silicon Bronze 5/8" Ground Clamp for demanding applications including direct burial, where the simple mechanical design and reliable clamping power of the screw outperform other options. GRC-family clamps with the -SB suffix have a body and screw made from silicon bronze for maximum strength, and the clamp is UL-listed for direct burial in earth or concrete. Stock products you can rely on—stock NSI.