What This 20-Position Header Does in the Build
The 5499923-4: The shrouded 4-wall housing with latch lock/eject hooks and a keying slot provides positive retention and polarization — the eject hooks lever the mating connector loose without prying at the housing wall, which matters in dense boards where finger access is tight. Contact finish is gold or gold-palladium on the mating surface at 15.0µinch (0.38µm) thickness, with tin on the solder posts (100.0µinch / 2.54µm).
The mounting flange and keying slot add mechanical stability and prevent mis-mating — the flange bolts down to the board for extra shear strength when the cable is routed under tension.
The 5499923-4 has 20 positions vs 4, a vertical orientation, and gold mating contacts vs tin — the tin-plated sibling is for lower-cycle, cost-sensitive applications where 1 A per contact is adequate.