'Way-in way-out vessel' equivalent to two Klein bottles, one inverted, sealed together back-to-back. When cut it forms two pairs of single twist Mobius strips.

A single surface model made by Alan Bennett in Bedford, 1995. This 'way-in-way-out vessel' is equivalent to two Klein bottles, one inverted, sealed together back-to-back. When cut it forms two pairs of single twist Mobius strips. A Klein bottle is a surface which has no edges, no outside or inside and cannot be properly constructed in three dimensions.