Three-dimensional sketch of GS305+04-26 and the star members of Cen OB1. The large Hi shell is shown as a dotted ellipsoid. The location of both pulsars is given by black squares. The open circles indicate the location of Cen OB1 members identified as such by Humphreys & McElroy (1984) and Corti & Orellana (in prep.) whilst the plus sign marks the position of those stars considered to be members of Cen OB1 only by Corti & Orellana (in prep.). The projection of the conical structure refered to in the text is also depicted.