Mobius strip is a finite surface much longer than wider that has twists and joins at the ends. If you cut this area through the middle you will get one surface twice longer and twice narrower than the first one.

Two dimensional figures (shadows and projections of three dimensional bodies) that have center of symmetry, after a complete tour on this surface they reversed (left hand becomes right and vice versa) but upside down.

Klein bottle is a three-dimensional body twisted so that the inside part comes outside. Both concepts have been used as an argument in favor of supporters of finite physical space.

Both, Klein bottle and Mobius strip are finite things contained in physical finite space. If physical space would be nothing but a larger bottle of Klein, as people say, then what is outside the bottle, is not there space as well?