If a smooth Möbius strip in three-space is a rectangular one – that is, created from identifying two opposite sides of a geometrical rectangle with bending but not stretching the surface – then such an embedding is known to be possible if the aspect ratio of the rectangle is greater than formula_10, with the shorter sides identified. (For a smaller aspect ratio, it is not known whether a smooth embedding is possible.) As the aspect ratio decreases toward formula_10, any such embedding seems to approach a shape that can be thought of as a strip of three equilateral triangles, folded on top of one another to occupy an equilateral triangle.