Handy for making wire harnesses or jumpering between headers on PCB’s. They have 0.1″ male header contacts on one end and 0.1″ female header contacts on the other. They fit cleanly next to each other on standard-pitch 0.1″ (2.54mm) header.
For best results, when plugging these in a line, have the sides with the ‘silver latch bit’ sticking out since that side is a tiny bit wider than 0.1″
Note: Retail price per piece.
This product and description is from Adafruit.