Phonograph records are generally described by their diameter in inches (12", 10", 7"), the rotational speed in rpm at which they are played (16 2⁄3, 33 1⁄3, 45, 78), and their time capacity resulting from a combination of those parameters (LP – long playing 33 1⁄3 rpm, SP – 78 rpm single, EP – 12-inch single or extended play, 33 or 45 rpm); their reproductive quality or level of fidelity (high-fidelity, orthophonic, full-range, etc.), and the number of audio channels provided (mono, stereo, quad, etc.).