This solution allows consumers a limited amount of private copies. The record labels can individually define the burn count. These copies are then also fully protected and offer the same efficiency and compatibility as the original disc. The audio sessions are being encoded to Windows Media Audio DRM-protected files, so that some portable devices are supported and online distribution prevented. Furthermore, with key2audioXS the user can now pick and send audio tracks via email. With a usability period defined by the record label, users can share music, facilitating promotion activities for labels. Additionally, some discs feature "n-CD", which lets the user access bonus features such as videos, ringtones, lotteries and the like. The original n-CD is a unique key reserved for just their owners. For this purpose, the user interface for key2Audio on PC allows for navigation and includes a copying and burning tool, as well as additional content such as bonus pictures and lyrics. The audio part can hold up to 75 minutes. Notes External links Key2Audio explained and should we fear it? Compact Disc and DVD copy protection