With its discovery and characterization of several hundreds sources, Fermi-LAT has revolutionized our knowledge and understanding of the BL Lac population with respect to other AGNs. The MWL picture has however not kept up the pace of the gamma-ray observations. We have selected an unbiased sample of 42 BL Lacs, independent of flux density and observed it at 8 and 15 GHz with the VLBA. We present the results of the observations and a statistical analysis of the jet properties in these sources, discussing flux densities, spectral indexes and other physical quantities.