  We examine the optical properties of the nuclei of low luminosity
radio-galaxies using snapshot HST images of the B2 sample. In agreement with
the results obtained from the analysis of the brighter 3C/FRI sample, we find a
correlation between fluxes (and luminosities) of the optical and radio cores.
This provides further support for the interpretation that the optical nuclear
emission in FRI is dominated by synchrotron emission and that accretion in
these sources takes place in a low efficiency radiative regime. In the
framework of the FRI/BL Lacs unified scheme, we find that the luminosity
difference between FRI and BL Lac nuclei can be reproduced with a common
beaming factor in both the radio and the optical band, independent of the
extended radio luminosity, thus supporting such a scenario. The corresponding
bulk Lorentz factor is significantly smaller than is expected from
observational and theoretical considerations in BL Lacs: this can be
interpreted as due to a velocity structure in the jet, with a fast spine
surrounded by a slower layer.
