The M3 Square nuts (2 each) are sized for the more commonly available size (2.3mm thick) - the Prusa nuts are slightly thinner (1.7 mm) and will slide out of the slots.
When used just to hold the buffer plates together, 2 M3x25 or M3x30 bolt will suffice. Use longer if mounting to something else of course.
Note that one end allows the bolt head to be flush, while the other is not as deep.
For use with the MMU3 buffer mount for the rear of the (Un)Original Drybox shown in the photo. https://www.printables.com/model/1180632-vertical-buffer-mount-for-rear-of-unoriginal-drybo
The author remixed this model.
I removed the tabs that allow mounting to a surface as they're not needed for my purposes.