Fridge magnet calibration cube

I end up with quite a few calibration cubes that really have no other use, so I set off to draw one up that had a cylindrical hole at the bottom - which I could glue a round magnet and then use it as a fridge magnet.

The standard calibration cube is too easy anyways for todays printers, so I added a few different faces to make it more challenging.

Comes in different sizes, for 4mm, 5mm and 6mm round magnets.