The 3.50 mm pitch provides enough spacing for moderate current without wasting board real estate.
The crimp termination means you build the wire assembly with the correct terminal — the housing itself is just the body. For a complete BOM, you need the plug housing, the crimp terminals for both halves, and the wire seals if the application requires sealing. The 3.50 mm pitch is consistent across the Multi-Lock series, so the mating half will share that pitch.
