This device used an endless plastic tape in a cassette. The tape was 16mm wide, with 56 parallel grooves. The tape needed to be flexible (to roll up) and at the same time hard enough to be read by a stylus. Pre-recorded tefifon tapes were first produced in the 1950's and had a playing-time of up to 240 minutes. These pre-recorded tapes were mainly of entertainment music. The tefifon technology had little success and disappeared from the market during the 60's.