Copper Bond Earth rods, Deep Driven, Usually Provide the most cost effective earth systems. They are made from a Low Carbon, High Tensile Strength 600N/mm² Minimum) Steel core with a coating of Molecular Bonded 99.9% Pure Electrolytic Copper. Extendable type rods have a Rolled Thread (UNC2A) at each end. Rolled thread have a Higher Strength than cut thread and also preserve the copper coating at the thread roots. Copper coating Thickness 250 Micron (Minimum).