Bubble memory started out as a promising technology in the 1980s, offering memory density of a similar order as hard drives but performance more comparable to core memory.
Bubble memory wound up as a choice for companies that wanted high-reliability mass storage or worked in environments where disk storage wasn't practical.
It had 128 kilobytes of internal memory (it was one of the few computers to use bubble memory), which could be expanded by the use of plug-in cartridges.