  We investigate the dust size and dust shell structure of the bipolar
proto-planetary nebula M 1--92 by means of radiative transfer modeling. Our
models consists of a disk and bipolar lobes that are surrounded by an AGB
shell, each component having different dust characteristics. The upper limit of
the grain size $a_\mathrm{max}$ in the lobes is estimated to be $0.5 \mu$m from
the polarization value in the bipolar lobe. The $a_\mathrm{max}$ value of the
disk is constrained with the disk mass (0.2 $M_{\sun}$), which was estimated
from a previous CO emission line observation. We find a good model with
$a_\mathrm{max}=1000.0 \mu$m, which provides an approximated disk mass of 0.15
$M_{\sun}$. Even taking into account uncertainties such as the gas-to-dust mass
ratio, a significantly larger dust of $a_\mathrm{max}>100.0 \mu$m, comparing to
the dust in the lobe, is expected.
  We also estimated the disk inner radius, the disk outer radius, and the
envelope mass to be 30 $R_\star$(=9 AU), 4500 AU, and 4 $M_{\sun}$,
respectively, where $v_\mathrm{exp}$ is the expansion velocity. If the dust
existing in the lobes in large separations from the central star undergoes
little dust processing, the dust sizes preserves the ones in the dust
formation. Submicron-sized grains are found in many objects besides M 1--92,
suggesting that the size does not depend much on the object properties, such as
initial mass of the central star and chemical composition of the stellar
system. On the other hand, the grain sizes in the disk do. Evidence of large
grains has been reported in many bipolar PPNs, including M 1--92. This result
suggests that disks play an important role in grain growth.
