[SOLVED] What's the difference between m.2 and ultra m.2?

[TooGreen]

What's the difference between m.2 and ultra m.2?

 

[SkyNetRising]

Ultra M.2 is Asrock marketing term for PCIE 3.0 x4 M.2.

On modern boards there's no difference (M.2 is already PCIE 3.0 x4).
On older boards like Z97 - M.2 was PCIE 2.0 x2. Then there was significant performance difference.