One of the most well-known uses of FourCCs is to identify the video codec or video coding format in AVI files. Common identifiers include DIVX, XVID, and H264. For audio coding formats, AVI and WAV files use a two-byte identifier, usually written in hexadecimal (such as 0055 for MP3). In QuickTime files, these two-byte identifiers are prefixed with the letters "ms" to form a four-character code. RealMedia files also use four-character codes, however, the actual codes used differ from those found in AVI or QuickTime files.