Positions of our sample of H-deficient stars in the Kiel diagram (large symbols), together with all previously known objects (whether or not associated with a PN) of the spectral classes PG1159 and O(He), as well as a number of DO WDs (small symbols). Evolutionary tracks (blue lines) for VLTP post-AGB stars labeled with the stellar mass in solar units are from Miller Bertolami & Althaus (2006). The solid and dashed black lines indicate two theoretical PG1159 wind limits, below which heavy elements settle out of the photosphere; for details see text.