When the standard 1x1 inserts are still too large I use these triangular bins. I found that the problem with bins with a subdivider is that the divider does not 'seal' well at the top or gets in the way of the index ribs in the lid. These triangular bins fit well in the Europlus Flex cases, also on the lid side.

The bottom of the bin has a thin and shallow hole so that the 3D-printed infill lines show where the feet (separate file) are to be glued under. The feet are separate for printability of the bins and also work well on the original printed Allit Europlus Flex Insert by Noloxs. For the triangular bins I use 2 feet, one of which is cut through using cutting pliers.

I printed the bins spiralizing using 0.8 mm wide lines.