PCIe compatibility

[SemperFitz]

Morning all,

I'm going to buy a M2 for my MSI B350 gaming pro MB, and started looking at various options/manufactures/pricing, but then i got confused with PCIe gens.

The spec on my MB says -

1 x M.2 slots (Key M)
- Supports PCIe 3.0 x4

and i was thinking of buying WD_BLACK SN850X, but that says -
PCIe Gen4

Are they compatible?

Yours confused

 

[SemperFitz]

thank you