Gridfinity holder for the Montana Brand 3pc Plug Cutter Set:
https://www.montanabrandtools.com/products/3pc-plug-cutters
Holds 5/16", 3/8" and 1/2" cutters.
Note this holder is 4U high so that it can be stacked while full, but does not line up with the more typical heights of 3U or 6U.
The author marked this model as their own original creation.