The top compartment is rectangular (43.5 cm x 21 cm) with a diagonal of 48 cm.

No. The length is 44.5 cm, but the width is only a little more than 20 cm.

if you measure inside, there is definitely room for 43 x 19 cm, as the box gets smaller towards the bottom and reinforcements get in the way

Hello, no, unfortunately a socket spanner set with the dimensions 44.5 x 21 just doesn't fit into the top compartment (certainly not flat), except perhaps at an angle. The internal dimensions of the top compartment are 20 x 44.5 (at/because of the lock) which may narrow slightly towards the bottom (difficult to measure). The drawers are narrower anyway. But why should a socket spanner set that is stored in a box go in this box? I also have my two large sets of socket spanners separately, partly because it's easier for me to access them and I prefer to use the box for my other tools, such as my drill (without its own box).

43x21x24 high is the internal dimension, so not likely, at most diagonally

Hello Ruedi, that's just not possible: 43.5 cm measured between the ribs. If you mill them away, it may work, but the box may no longer be stable. There are 5 Bauhaus specialist stores that stock the smaller brother, the top toolbox should be identical: Art. 22099127. I recommend trying out the toolbox there with your socket spanner set. Greetings pp0883

In any case