These female-female premium jumper wires are handy for making wire harnesses or jumpering between headers on PCB's. They're 3" (75mm) long and come in a 'strip' of 20 (2 pieces of each of ten rainbow colors). They have 0.1" female header contacts on either end and fit cleanly next to each other on standard-pitch 0.1" (2.54mm) header. The best part is they come in a 20-pin ribbon cable. You can always pull the ribbon wires off to make individual jumpers, or keep them together to make neatly organized wire harnesses.
For best results, when plugging these into a male header, have the sides with the 'silver latch bit' sticking out since that side is a tiny bit wider than 0.1".