99.9 % pure electrolytic copper molecularly bonded onto a steel core in accordance with national and international standards to a thickness of 0.25 mm. Note : Rods are not of the sheathed type. There is no metal interface. So dissimilar metal reaction cannot occur and the copper cannot be separated from the steel. The core is of low carbon steel of grade 080A20 of BS970 with a high tensile strength of at least 600 n / mm2. Threads are rolled onto the rod which ensures that an even copper covering is maintained, even at the root of the thread.