Klein bottle
thingiverse
Klein Bottle is a solid object that does not have a wall thickness, so inverting polygons will not allow you to create it fully for 3D printing. But it will be possible to approach it in this way, so as not to turn it into a vase.
Download Model from thingiverse
With this file you will be able to print Klein bottle with your 3D printer. Click on the button and save the file on your computer to work, edit or customize your design. You can also find more 3D designs for printers on Klein bottle.