Board Fit and MTA-100 Series Position
The 3-644695-8: The unshrouded design means no polarizing wall; the mating MTA-100 receptacle housing provides the keying and latch.
Current Rating and Wire Gauge Dependency
In the MTA-100 system, the crimped terminal and attached wire set the thermal ceiling. For a harness designer, this means the 8-position header can carry signal-level loads or moderate power, but the per-circuit current must be derated based on the wire size and ambient temperature.
Peer Comparison: 1-292164-1
The closest functional second-source is the TE CT series header 1-292164-1, which is also a single-row unshrouded header but with an 11-position count on a tighter 0.079" (2.00mm) pitch and a right-angle orientation. Its voltage rating is 125 VAC, half this MTA-100's 250 VAC. If your board layout and BOM allow 2.00mm pitch and need more circuits, that part is a viable alternative; if you need the 2.54mm pitch or the full 250 VAC rating, stick with the MTA-100.