45 RPM records are a type of vinyl record that play at a speed of 45 revolutions per minute. They were introduced in the late 1940s and became popular for single songs, often featuring one track on each side. The standard size of a 45 RPM record is 7 inches in diameter. These records are known for their distinctive large center hole, which allows them to be played on specific turntables. 45 RPM records often feature popular music from various genres, making them a favorite among collectors and music enthusiasts.