0.40 mm pitch — the footprint is the constraint
The part sits 0.026" (0.65 mm) above the board and mates to a 0.8 mm stack height, which sets the z-axis clearance for the enclosure. The center strip contact arrangement and dual-row layout (2 rows) pack 40 circuits into a narrow body.
Solder retention — what it means on the line
The 5055504020 includes a solder retention feature. On a 0.40 mm pitch SMT part, the risk during reflow is tombstoning or shift from uneven solder paste wetting. The retention pads hold the connector in place through the oven profile, so you don't need a separate adhesive dot or a secondary press operation. It's a small detail that saves a rework step on a high-density board.