The Molex 5031104000 is a 40-position plug housing from the Duo-Clasp 503110 series.
The 1.25mm pitch is fine enough to route dense signal bundles but still allows hand-crimping with standard tools — no micro-coax termination required. The plug is keyed by its own geometry — no keying pin to lose.
Contacts are not included in this order code; order the male crimp terminals separately (Molex part number for the terminal is available in the series datasheet). The free-hanging design lets you route the harness before mating to the board-mounted header.