Silver Plated Copper Clad Steel (SPCCS) commonly used for RF coaxial cables) as per ASTM-B-501 Spiral multi-strands on glass-fibre cord for high linear resistance -- generally for heating applications Plain copper or Tinned copper can not be used due to high-temperature processing and applications; tin melts and flows into the interstices of stranding to make the conductor inflexible; copper tends to oxidize and become brittle