Originally from the Harmonic Technology website. . .
The conduction wire is a bi-metal hybrid, consisting of four filaments to optimize both bass and treble frequencies. Half of the filaments are designed for the midrange/treble signal and consist of two isolated strands of pure silver, cast to a purity level of 7N (99.99997%) and of course, is made with Single Crystal TM (OCC) technology. The remaining two filaments consist of Single Crystal copper and optimize the bass range, adding a fuller tone quality. The braided outer shield is pure silver plated on copper and was designed to isolate the delicate signal from RFI noise fields. A second defense noise barrier is provided in the form of an aluminum-coated Mylar shield situated closer to the conductors to ensure a very high signal-to-noise ratio.
This Twin-Shield design will give you the ultimate in clarity and 3-D imaging with a velvety-black background silence due to elimination of electromagnetic interference, whether generated by RFI (radio frequency interference), digital noise, or A.C. generated hum. All insulation consists of either Teflon tape or air-foamed PE (polyethylene using the air bubbles as the main dielectric).