The team at Chiphell have shown off some images of what appears to be low profile DDR4 ECC RAM. The RAM comes in a single 4GB stick at 2133MHz with timings of 15-15-15, measuring at a tiny 18.75mm which make them about 40% smaller than normal sticks of RAM.
If you were thinking of getting some these for your machine at home then you'd have to save up around £275.57 each stick.
Source: www.chiphell.com and mydrivers.com