Tinned copper....Soft tinned copper complies with A. S. T. M. B33.

Silver-plated.... Minimum of 40 micro-inches of silver. For use where the wires are subjected to temperatures exceeding 200° C or if special corrosion resistance is required.

Nickel- plated....Minimum of 50 micro-inches of nickel. For use where the wires are subjected to temperatures up to 450° C or if special corrosion resistance is required.

Stainless steel....Wires conform to MIL-W-423, composition 304. For use where wires are subjected to temperatures up to 650° C or where mechanical strength and protection are important considerations.