The TE Connectivity 5353185-8 is a 100-position plug from the Free Height (FH) series, designed as the top half of a board-to-board mezzanine interconnect. The connector sits 0.214" (5.45mm) above the board and mates to a corresponding Free Height receptacle at a 4mm stacking height — that 4mm figure is the z-height budget between parallel PCBs, so it decides the card spacing before you lay out the board.
The board guide aligns the connector during pick-and-place, and the solder retention anchors it through reflow — without that retention, the connector can shift under the shear load of a cable or mating cycle.
It's a current BOM line part, not a last-time-buy scavenge.