Klein Bottle

Print in the default orientation, standing straight up. It should be relatively easy to print except for the top of the model where the tube is horizontal.

I printed with a 0.1mm layer height to assist the bridging, and had exceptional results despite the severe overhang. You could get away with a greater layer height if you use supports.

There are two models. "Klein_Bottle.stl" has a rounded base which may feel more natural, but the bottom curves make it difficult to print. "Klein_Bottle_Easy_to_Print.stl" has a flat base. I recommend using the latter.

At full scale, the tube has an inner diameter of 24mm. I printed at 75% size which is the perfect dimensions for a standard marble (~15mm diameter marble) to fit through.