40-position 2.54mm pitch header — BOM-fit anchor
Shrouding, keying, and eject hooks — handling in dense layouts
The keying slot prevents inserting the mating half in the wrong orientation, which saves rework in a harness build. Long latch lock/eject hooks provide positive retention against vibration and a mechanical lever to unmate the connector without prying on the housing. This is a practical advantage in a backplane or panel where the header is recessed and finger access is tight.
Sourcing and lifecycle — active, RoHS, bulk packaging
RoHS compliant without exemptions — no lead, cadmium, or restricted phthalates in the housing or plating. The tin post finish is matte tin over nickel, standard for lead-free solder processes.
Comparing 40-position vs 30- and 34-position siblings
The closest functional alternative is the 30-position 5499922-7, which shares the same 2.54mm pitch, gold mating finish, long eject hooks, and UL94 V-0 housing — only the position count differs. If your BOM calls for 30 circuits, that is a direct drop-in; if you need 34 circuits, the 5499910-8 uses short eject hooks instead of long, which changes the unmating tool clearance.