  While in the past spheroidicity was assumed, and still is used in modeling of
most nebulae, we know now that only a small number of planetary nebulae (PNe)
are really spherical or at least nearly round. Round planetary nebulae are the
minority of objects. In case of those objects that underwent a very late helium
flash (called VLTP or "born-again" PNe) it seems to be different. The first,
hydrogen rich PN, is more or less round. The ejecta from the VLTP event is
extremely asymmetrically. Angular momentum is mostly assumed to be the main
reason for the asymmetry in PNe. Thus we have to find processes either changing
their behavior within a few hundred to a few thousands of years or change their
properties dramatically due to the variation of the abundance. They most likely
have a strong link or dependency with the abundance of the ejecta.
