This case fits the Raspberry Pi 4 with the HiFiBerry DAC (RCA versions), Digi or Amp. It is very simply to mount without additional tools. Just plug plug the HiFiBerry card onto your Raspberry Pi and snap it into the case.
Note that this case won’t fit perfectly for boards with an onboard phone-jack (e.g. DAC2 Pro). With these, you need to slightly bend the board upwards.