  The black hole mass and spin estimates assuming various specific models of
the 3:2 high frequency quasi-periodic oscillations (HF QPOs) have been carried
out in Torok et al. (2005, 2011). Here we briefly summarize some current
points. Spectral fitting of the spin a=cJ/GM^2 in the microquasar GRS 1915+105
reveals that this system can contain a near extreme rotating black hole (e.g.,
McClintock et al. 2011). Confirming the high value of the spin would have
significant consequences for the theory of the HF QPOs. The estimate of a>0.9
is almost inconsistent with the relativistic precession (RP), tidal disruption
(TD), and the warped disc (WD) model. The epicyclic resonance (Ep) and
discoseismic models assuming the c- and g- modes are instead favoured. However,
consideration of all three microquasars that display the 3:2 HF QPOs leads to a
serious puzzle because the differences in the individual spins, such as a=0.9
compared to a=0.7, represent a generic problem almost for any unified orbital
3:2 QPO model.
