  Quasar microlensing flux ratios are used to unveil properties of the lenses
in large collections of lensed quasars, like the ones expected to be produced
by the Euclid survey. This is achieved by using the direct survey products,
without any (expensive) follow-up observations or monitoring. First, the
theoretical flux ratio distribution of samples of hundreds of mock quasar
lenses is calculated for different Initial Mass Functions (IMFs) and Sersic
radial profiles for the lens compact matter distribution. Then, mock
observations are created and compared to the models to recover the underlying
one. The most important factor for determining the flux ratio properties of
such samples is the value of the smooth matter fraction at the location of the
multiple images. Doubly lensed CASTLES-like quasars are the most promising
systems to constrain the IMF and the mass components for a sample of lenses.
