These are custom made to adapt the wiring for the HP Z400 non-standard motherboard wiring for standard ATX PC style power supplies. Do not use a regular ATX PSU for the HP Z400 motherboard without this adapter. It will fry the HP motherboard.
This sale is for one:
HP Z400 PSU Conversion Adapter
24-Pin Male to 24-Pin Female Adapter
Convert a regular PC style power supply for the HP Z400 Workstation.