What this 1.25mm pitch right-angle header does in the assembly
The 1.25mm pitch keeps the footprint compact — five signals fit in about 6.25mm of board edge — and the right-angle orientation lets the mating cable lie flat against the board, which matters in tight enclosures. For a one-time or low-cycle assembly, it's fine.
Where this header fits in the HPI series and what it mates with
The HPI series spans a range of positions and pitches; the 1734829-5 sits at the compact end with 5 circuits and 1.25mm pitch. Compared to a sibling like 1394090-1 — a 6-position header at 2.85mm pitch with a latch holder — this part is narrower in pitch and position count, so it targets denser, lower-current signal runs. The 1394090-1's latch holder adds vibration retention; the 1734829-5 relies on the 4-wall shroud for alignment, not a locking feature.