The 10129378-936003BLF: The header is cuttable — you can break the strip to a custom length, which simplifies BOM management if your design uses multiple position counts. Gold on the mating interface keeps contact resistance stable across repeated mating cycles — useful for test fixtures or field-service connections where the header is disconnected and reconnected regularly. This covers most indoor industrial and telecom environments.
This is common for board-to-board stacking or cable-to-board connections where the mating half aligns mechanically through the enclosure or a separate alignment feature.