Stereo 8, was more commonly known as eight-tracks. It was a magnetic tape with 8 tracks. They were popular from the mid 60's to early 80's.
Stereo 8, commonly known as the eight-track cartridge, eight-track tape, or simply eight-track, is a magnetic tape sound recording technology. It was popular in the United States from the mid-1960s through to the early 1980s, but was relatively unknown in many European countries. It was, however, very popular in the United Kingdom during this period. Stereo 8 was created in 1964 by a consortium led by Bill Lear of Lear Jet Corporation, along with Ampex, Ford Motor Company, General Motors, Motorola, and RCA Victor Records (RCA). It was a further development of the similar Stereo-Pak four-track cartridge created by Earl 'Madman' Muntz. A later quadraphonic version of the format was announced by RCA in April 1970 and first known as Quad-8, then later changed to just Q8.
Contributions by ProhibitOnions, Blainster, and GRAHAMUK.