Sometimes just referred to as metal tape, a type of magnetic tape that uses microscopic particles of iron rather than iron oxide as the magnetic medium. Metal tape is capable of much better performance than oxide tape, especially at high frequencies, but it requires a different equalization and bias. The improvement is most pronounced at low tape speeds, which is why it has been such a popular formulation for cassette tapes. The disadvantage of metal particle tapes is that they tend to be a little less flexible and more abrasive to the heads, causing both more shedding and head wear. Newer machines employ tape heads specifically designed to be used with this tape.