Prepare to waste at least 3 mins trying to figure this thing out. It is called the "Klein Bottle" and has no inside nor outside surface, what is more you can actually fill these with fluid.
Here's how
seen from France
seen from United States
seen from United States

seen from United States
seen from Malaysia
seen from United States

seen from Germany
seen from United States
seen from United States
seen from Malaysia
seen from Portugal
seen from United States
seen from United States
seen from United States
seen from United States

seen from United States

seen from Philippines

seen from Singapore

seen from Germany

seen from United States
Prepare to waste at least 3 mins trying to figure this thing out. It is called the "Klein Bottle" and has no inside nor outside surface, what is more you can actually fill these with fluid.
Here's how