What this MTA-156 3-position IDC receptacle is
The 0.156" (3.96mm) pitch is the defining footprint dimension — it matches the standard MTA-156 header pin spacing, so the board layout is fixed once that header is placed. The orange closed-end housing blocks the last cavity, preventing a stray terminal from being inserted and leaving a live contact exposed at the end of the harness.
It accepts 18 AWG wire, either discrete or ribbon cable. The tooling required is the standard MTA-100/MTA-156 hand tool or a bench press with the appropriate IDC head; the same tool family covers the whole MTA series, so if you already build MTA harnesses, the setup is identical.