Gridfinity holder for Central Forge 12 PC Needle File Set
The twelve holes are 9.5mm in diameter and 36mm deep.
If you want to install M3 bolts in the bottom, just punch through the thin skin above the magnet/bolt holes
Remixed from https://www.printables.com/model/210548-filled-in-gridfinity-boxes-for-customization
Gridfinity:
The author remixed this model.