Klein bottles, 1995..

A Klein bottle is a surface with no edges, no outside or inside, which cannot be properly constructed in three dimensions. These examples were made by Alan Bennett in Bedford, United Kingdom. Left: three Klein bottles share an inlet tube which when cut produces three pairs of single-twist Mobuis strips. Middle: Klein bottle with inlet passing through vessel which when cut forms a pair of single-twist Mobius strips. Right: three Klein bottles in a column which when cut form a pair of five-twist Mobius strips.