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tokens: spectra, the instrumental differences in spectral observations render the SEDs globally more homogeneous. To compare these to models, we made use of the VO SED Analyzer (VOSA; Bayo et al. 2008 ) which provides χ 2 and Bayesian fitting to an array of models and templates. For this data, we adopted the χ 2 fitting to BT-Settl models (Allard, Homeier Freytag 2012 ) with the following limits: 700 T eff 4000 K, and . We also limited the absorption in the V band to 0.001 and turned off the excess fitting option as the non-black body distribution of the spectra of these objects was causing the excess fitting procedures to ignore the mid-IR magnitudes. As an example in Fig. 5 , we plot the VOSA fit of 0227-1624 to the BT-Settl model spectra. 0227-1624 is a 16th -band magnitude L1/L0.5 object at 20 pc with a 8 per cent error on the distance for which we have magnitudes in 11 bands. The model slightly underestimates the near- and mid-infrared bands but follows well for the optical bands. Reasons for this over luminosity are beyond the scope of this paper as it will require a more in-depth study of the models and the fitting of VOSA. Figure 5. An example VOSA χ 2 fitting of the 0227-1624 spectral energy distribution to BT-Settl models. The optical to J bands appear to fit well but the model underestimates the flux in the other near and mid-infrared bands reasons for which are discussed in Section 4.4 . The Gaia G observation is plotted in orange because we manually removed it from the fit. We find the nominal G passband tends to over estimate the flux of the L and T dwarfs which can be seen in Fig. 5 . This systematic excess is also reflected in the model (the blue points) as this uses the G passband for the transformation, however, we felt this known systematic error made using the Gaia magnitude for the 38 objects in the Gaia DR1 to constrain the fits premature. The problem of the G passband is noted in the Gaia documentation, 2 and there is an empirical correction proposed(Maíz Apellániz 2017 ). In Fig. 6 , we plot the RAD1 radius from the VOSA fits to BT-Settl models against the near-infrared spectral types. RAD1 is the ‘scaling radius’, i.e. the radius required to fit the observations to the model based on the parallactic distance. From the PARSEC sample, we removed all objects which are known or suspect unresolved binary systems and known or candidate moving group objects (see Section 5.3 ) leaving 60 objects. We removed the moving group objects as these are in general young and we wanted to be sure that our sample was dominated by objects older than 1 Gyr. In Fig. 6 , the targets plotted as diamonds are literature objects and the PARSEC sample are plotted as asterisks. The radius of objects with ages greater than 1 Gyr in this spectral range is predicted to be a minimum at the spectral type that corresponds to the hydrogen burning limit (e.g. Chabrier et al. 2009 ; Burrows, Heng Nampaisarn 2011 ). Objects with earlier spectral types than this