Update April 2022: I know the walls are a bit thicker and it takes ages to print, but the boxes are really sturdy and suitable for use on a contruction site. I print these boxes with my leftover or faulty material, so they come in all colours and don't cost me much.
Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:4530024.
Thes boxes are an addition the the factory made boxes by Sortimo. The idea is to make inserts 1.5, 2.5, 3.5 (and so on) times of the normal grit, to make better fitting boxes and to make more use of the existing space in the containers. Haven't seen them here or somewhere else so I decided to share the idea.
I make them in full and half (of the height) and stack them on top of each other if I need to. The pegs are moved to the furter next position to be able to use the grit/ pegboard inside the containers.