The LP is an analog sound storage medium, specifically a phonograph record format characterized by a speed of 33+1⁄3 rpm, a 12- or 10-inch diameter, use of the "microgroove" groove specification, and a black vinyl composition disk. Introduced by Columbia Records in 1948, it was soon adopted as a new standard by the entire US record industry and, apart from a few relatively minor refinements and the important later addition of stereophonic sound in 1957, it remained the standard format for record albums during a period in popular music known as the "album era". LP was originally a trademark of Columbia and competed against the smaller 7-inch sized "45" or "single" format by RCA Victor, eventually ending up on top. Today in the vinyl revival era, a large majority of records are based on the LP format, and hence the LP name continues to be in use today to refer to new records.