The type of ferric oxide compound that is used in the manufacture of magnetic recording tape.
"I received my 3 CDs that you made from my cassettes. The sound quality was much better than I had expected. My songs had a lot of strings in them and a clear / high note sound was very important to me. Your CD copies kept the strings nice and clear with sharp tones just as I had wanted. Thanks, good job!! I also noticed where some LP pops and ..."