Transcription discs are most commonly 16 inches (40 cm) in diameter and recorded at 33 1/3 rpm. That format was standard from approximately 1930 to 1960 and physically distinguishes most transcriptions from records intended for home use, which were rarely more than 12 inches (30 cm) in diameter and until 1948 were nearly all recorded at approximately 78 rpm. However, some very early (circa 1928-1931) radio programs were on sets of 12 inch (30 cm) or even 10 inch (25 cm) diameter 78 rpm discs, and some later (circa 1960-1985) syndicated radio programs were distributed on 12 inch (30 cm) diameter 33 1/3 rpm microgroove vinyl discs visually indistinguishable from ordinary records except by their label information.