The 1-794040-1: This is a 12-position, 3-row vertical header on 0.163" (4.14mm) pitch — the same pitch as the row spacing, so the contact grid is square. The shrouded 4-wall housing guides the mating receptacle and keeps the pins from bending during blind-mate assembly.
Current, Voltage, and Environment
Rated 600VAC — the limiting factor is the creepage distance through the nylon housing, not the contacts themselves.
How This Compares to 1318699-3
Key differences: 1318699-3 uses a 0.165" (4.20mm) pitch (slightly wider), is rated 250VAC (not 600VAC), has a latch lock instead of a locking ramp, and uses phosphor bronze contacts with only 3.00µin gold. If your application needs the full 600VAC rating or the board lock feature, 1-794040-1 is the correct choice.