The flexi disc (also known as a phonosheet or Soundsheet, a trademark) is a phonograph record made of a thin, flexible vinyl sheet with a molded-in spiral stylus groove, and is designed to be playable on a normal phonograph turntable. Flexible records were commercially introduced as the Eva-tone Soundsheet in 1962, but were previously available in the Soviet Union as "rentgenizdat", "bones" or "ribs", underground samizdat recordings on x-ray film.
en.wikipedia.org/wiki/Flexi_disc
