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Product Name: Klein Bottle 4D
The Klein bottle is a geometrical object, named after the German mathematician Felix Klein. He described it in 1882, and named it Klein’sche Fläche (Klein surface).
Because the surface is non-orientable, there is no “inside” or “outside”. This means that if a liquid were filled “in the bottle”, it would run down its surface.
How To Fill a Klein Bottle The Easy Way？