"C 90" Memorex cassette, high bias, one of two, as available commercially, 1980.

Memorex C90 Oxide high quality ferric cassette tape wound to C90 length, so 45 minutes per side, with Type I / Ferric tape. These tapes were commercially available in the 1980s, both as pre-recorded tapes and tapes that could be recorded. Casette tapes of this type could be listened to on "boom box" sound systems through loudspeakers; on Walkmans and other portable music devices which could listened to with headphones; and in casette players in cars.

Repeated plays could cause the casette tape to become entangled in the playing mechanism. This could be fixed by using a pencil to roll back the tape head and so return the casette tape to the plastic casette.