Like the 33⅓ rpm record, the 7-inch 45 rpm record used microgrooves, allowing a similar playing time to the 10-inch 78 rpm records it partly replaced.
RCA initially used eight different colours of vinyl to indicate the genre of the music, with popular releases on black vinyl, children’s records on yellow vinyl and classical music on red vinyl for example. This didn’t continue as coloured vinyl was more expensive to produce, although coloured vinyl is still used for some special editions by different record companies.
Until 1950, a ‘War of the Speeds’ took place, and consumers were unsure which of the two new formats would prevail. In the end, the 12-inch long-play (LP) record became the predominant format for music albums, while the 7-inch 45 rpm become predominant format for singles, with a song on each side.
The 7-inch 45 rpm format was also used for the Extended Play (EP) record from 1952, which achieved up to 7½ minutes of playing time per side at the expense of lower volume by reducing the width of the grooves. These generally contained between three and six songs.
Outside of the US, 7-inch singles generally had small centre holes, like an LP, but a central section could be punched out (such as for use in jukeboxes). Inserts or adaptors were available to allow the use of 7-inch singles with a larger centre hole to be used in standard record players. Many record players of the 1950s and 60s had a tall centre spindle that allowed records to be stacked, to play a number of 7-inch singles in sequence.
In the UK, sales of the new 7-inch single format surpassed those of the 78 rpm record by 1958. By the 1980s however, 7-inch vinyl records were competing with cassette singles, CD singles, and later with downloads, and by 2012 accounted for around 0.1% of all single sales, although this still represented sales of around 96,000 copies.