Optical discs are the ideal solution for long-term, secure storage of your important files - ideal for your precious photos, videos and documents that you want to keep forever. Not only are they dust and water resistant, but they can also withstand severe fluctuations in temperature and humidity. The double/dual recording layer was made possible by creating a new... substrate layer that is sandwiched between each recording layer. This allows the laser beam to record on both layers. When the first layer has been written, the laser writes to the second layer. 8.5GB capacity on a single disc!