Yes. half height pcie card.
Strongly recommend to have an option of a cooling fan for PCIE compartment in the future. Not included, but as an option, well designed.
While mellanox cx3 may be super cheap and I'm totally okay with baking one of them and replacing if it dies(so far it didn't, im running mlx354 with two arista 40g-univ transceivers installed in p320 tiny, and no cooling), a better and newer cards would be an expensive replacement if it fries.
I have all but one m.2 storage accessed remotely over iscsi, which eases the overall thermal load on the system. I desperately need at least one pcie gen4 x16 lane slot for installing a much faster NICs for NVMEoF. That are vastly more expensive to lose, hence the active cooling of pcie bay is really an option I'd pay for.