26-circuit shrouded header with keying slot
The 66506-074 is the 26-circuit member of Amphenol ICC (FCI)'s Quickie header line, a shrouded 4-wall board-to-cable/wire header with a keying slot to prevent mis-mating.
Shrouding and keying for board-to-wire fit
The 4-wall shroud and keying slot protect the pins during mating and prevent insertion of a mismatched housing — the mating half must carry the complementary keyway.