Sony is known for their reliable and proven Optical Disc technology. Many of us have countless numbers of their XDCAM discs on our shelves serving as an archive, just like we used to do with tape stock. Sony has recognized the need to archive material in a larger format with the same reliability (up to 50 years based on testing), so they built an Optical Disc Cartridge, which combines 12 discs into one container, sort of like a car CD changer. Cartridges come in sizes up to 1.5 TB, in either write-one or re-writable formats.