A 5x2x6 Divider for holding breadboard jumper wires. It has 14 slots of varying lengths for holding each size with a minimum slot size so you can still fit a finger in. Every opening has a ramp, so no trouble getting even the last little jumper wire out with your fingers. I made it for this set from Amazon, but I'm sure it would work with many others as well.

An extension of #GridFinity, open sourced by Zach Freedman: https://www.youtube.com/watch?v=ra_9zU-mnl8