The GXT option is a palladium-nickel alloy underplate that extends wear life further, though both grades handle repeated connect/disconnect better than a tin finish would. For a field-service technician swapping boards in a test rack, this header will hold up through many insertions without fretting the contact.
Termination is through-hole solder — the pins pass through the board and are wave-soldered or hand-soldered on the opposite side. Overall contact length is 0.568" (14.43 mm), with the mating pin extending 0.318" (8.08 mm) above the insulation. That exposed pin length is what the receptacle contacts wipe against.
For a procurement buyer filling a BOM line, this is a stable part to commit: the BERGSTIK II series has been in the catalog for years, and the 6-position single-row variant is a common line item.