10-position MTA-100 header, 8 loaded
The 643879-6: This is a TE MTA-100 vertical through-hole header with 10 positions on a 0.100" (2.54mm) pitch, but only 8 are loaded with pins. The two empty spots are moulded in — the housing has 10 cavities, the contacts stop at position 8. Check your BOM position count before you lay out the board. Single-wall shrouding leaves three sides of the pins exposed; the header is keyed by the wall orientation, not a full shroud.
Tin-plated contacts, 250 VAC line
Tin-on-tin mating finish keeps the cost down for moderate-cycle applications — expect a few dozen mate-unmate cycles before the tin wipes through.