From Wikipedia:
The high-end audio cable industry markets oxygen-free copper as having enhanced conductivity or other electrical properties that are significantly advantageous to audio signal transmission. However, conductivity specifications for common C11000 Electrolytic-Tough-Pitch (ETP) and higher-cost C10200 Oxygen-Free (OF) coppers are identical.[8] Much more expensive C10100, a highly refined copper with silver impurities removed and oxygen reduced to 0.0005%, has only a one percent increase in conductivity rating, insignificant in audio applications.[8] OFC is nevertheless valued by audiophiles for both audio and video signals in audio playback systems and home cinema.