These are boxes that can be stacked one on another, or side by side. The smallest of these boxes is 50x50x50 mm.

1x1: Dimentions 50x50x50 cubic mm
2x1: Dimentions 100x50x50 cubic mm
2x2: Dimentions 100x100x50 cubic mm
3x1: Dimentions 150x50x50 cubic mm
3x2: Dimentions 150x100x50 cubic mm
3x3: Dimentions 150x150x50 cubic mm

I will add the grid soon, so you can secure them side by side.