The most common form of the vinyl single is the 45 or 7-inch. The names are derived from its play speed, 45 rpm, and the standard diameter, 7 inches (18 cm).
The 7-inch 45-rpm record was released 31 March 1949 by RCA Victor as a smaller, more durable and higher-fidelity replacement for the 78 rpm shellac discs. The first 45-rpm records were monaural, with recordings on both sides of the disc. As stereo recordings became popular in the 1960s, almost all 45-rpm records were produced in stereo by the early 1970s.