It has a eMMC sodered on Solid stade drive, there are models with 16GB or 32GB disks. The latter one beeing a little bit more rare. But, it does have a SD-card slot that supports storage extension, but probably not the answer you're looking for.
I've been looking into a possible mother board swap that would work in the stock enclosure, or at least with some modification but i haven't come to find anything suitable yet since i live in the EU and customs for every motherboard that might be compatible (at least physical) gets more than economically viable to order from the US.