This is a Gridfinity box made to contain a set of 20 pieces. the bottom ones to be placed are 12 mm, 10mm, 8 mm, 6 mm, you can place all the other barrs on the top of these and save a lot of space  in a 4 cm  wide box instead of a 14 cm. Many jewellers know that the lack of space to put the tools in drawers is a big issue.