I use this in conjunction with a demagnetizing tape head cleaner cassette.  Both are the same exact thing except that this one has no rotating magnet in it.  I wet this cassette with plenty of cleaning fluid and it improves the quality of my playback after playing filthy old cassettes.  I play it with the dry demagnetizing tape to dry it off and polish it while demagnetizing it.  I recommend this tape in conjunction with a demagnetizing head cleaner cassette as well.