Model of an ambiguous solid.
Look at it from one direction it appears to be a cubes, and from the opposite it appears to be a cylinders. Hold it up to a mirror and you see both at the same time.
The 6x model is a group of six of the shapes merged together to produce the illusion of either eight connected cubes or two full cylinders and six half cylinders.
Printed with 3 shells to get no infill as infill on this many thin walls would probably cause issues with retraction. Used Cura with line support at 20%. Use the preview to make sure your support lines are perpendicular to the walls of the object.