An optical disc is a type of storage media that consists of a flat, round, portable disc made of metal, plastic, and lacquer that is written and read by a laser. (The spelling, disk, is used for magnetic and flash memory media, and disc is used for optical media.) Optical discs used in personal computers are 4.75 inches in diameter and less than one- twentieth of an inch thick. Smaller computers, game consoles, and mobile devices, however, often use mini discs that have a diameter of 3 inches or less.