  The idea that, after their evaporation, Planck-mass black holes might tunnel
into metastable white holes has recently been intensively studied. Those relics
have been considered as a dark matter candidate. We show that the model is
severely constrained and underline some possible detection paths. We also
investigate, in a more general setting, the way the initial black hole mass
spectrum would be distorted by both the bouncing effect and the Hawking
evaporation.
