This 255mm (10 inch) storage cube can not only be used to hold GraviTrax pieces, but you can also build GraviTrax on the sides and bottom face of the box. A GraviTrax baseplate grid is built into the cube. The cube's walls are 5mm thick, which is plenty strong if you're using it to store plastic GraviTrax pieces. But don't use it like a regular milk crate to carry heavy items. The GraviTrax hex openings on the box are designed to grip GraviTrax tiles pretty well.

This cube is sized to just barely print on a Bamu Lab A1 3D printer, but is not printable on an X1C or P1S due to their exclusion zones, unless you follow the instructions in this instructional: https://wiki.bambulab.com/en/knowledge-sharing/print-volume-limitations.

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The box prints without supports, but I recommend slowing down the overhang print speeds. If printed with a shinier filament like the one in the pictures, you might want to dial down the outer wall acceleration and outer wall print speeds to ensure a good finish. I got some ringing on the one I printed, but it would not have been noticeable with normal PLA. I used Bambu Iridium Gold PLA which is a bit more shiny.

It requires 561g of filament to print, so it will cost about $12 to print depending on your filament cost.

SIDE NOTE ON 2ND VERSION:
I have another version of the box that I think is more aesthetic, designed without the filled in areas of this box, But while the model saves on filament at 488g, it requires snug supports on the model itself for a total of 700g of filament, and I'm not sure if the supports on the model will be easy or worthwhile to remove. I'm printing it now. Tree supports would not slice successfully in Bambu Studio because it placed supports outside the build plate. But if this prints turns out ok and the supports are easy to remove, I will post the other version.

Sorry, I didn't make the box stackable. This is still at the "huh, this might be a neat idea" stage. However, by gluing GraviTrax tiles in the top row of holes as shown in a couple of the photos, they would act as a lip for stacking another box on top.

Enjoy!