Prior to 1930, records were played on players such as the Victrola gramophone. These players, powered by electricity, spun the records at a consistent speed of 78 revolutions per minute (rpm). In 1930, RCA Victor produced the first commercially available long-playing vinyl record, which were called "Program Transcription" discs. The discs were pressed on flexible plastic and were designed to be played at 33 1/3 rpm. These discs were a commercial failure, largely because of the high costs of playback equipment and the growing popularity of radio during the Great Depression. With no viable alternative on the market, the discs known as 78s continued to be widely used until 1948, when Columbia introduced its 12-inch vinyl "Long Play" records. These LPs were played at a speed of 33 1/3 rpm and were commonly called "33s."
In 1949, RCA Victor released the first 45-rpm single. The 45s had a diameter of 7 inches, smaller than 12-inch LPs. Like the LP, these 45s were double-sided. While an LP could accommodate more than 20 minutes of playing time on each side, the 45s were meant to hold just one song per side. The 45s had a larger center hole than LPs to accommodate automatic mechanisms designed to drop one record at a time after each play.
In the mid-1950s, American record companies banded together to institute a standardized recording format, and the 33- and 45-rpm discs eventually became the industry standard. The 45s, also called "singles," only contained about five minutes of playing time per side. The LPs, however, eventually contained up to 30 minutes on each side. Record players produced after that time typically had speed settings to accommodate LPs, 45s and 78s. Records were placed on the player's revolving surface with the small spindle going through the record's center hole. However, the larger center holes of 45s required an adapter, a plastic snap-in insert called a "spider," before they could be played on a standard record player.
Both 45s and 33s were predominantly used for recorded music. The recording time available on a 33 record allowed for numerous songs, while a 45 typically featured one song on each side. During the 1950s and early 1960s, the popularity of rock 'n' roll music increased the popularity of 45 singles. At that time, teenagers were typically more interested in listening to a performer's hit single than the entire album, and 45 singles were typically far less expensive than LPs.