  The spectral energy distribution (SED) of blazars is generally understood
through the standard one-zone synchrotron self-Compton (SSC) model, where a
strong correlation between X-ray and TeV gamma-ray fluxes is expected.
Recently, for Mrk 421 the correlation was confirmed and interpreted within the
SSC model arguing that a description of the correlation up to large flux values
considerably restricts the value of the magnetic field under the assumption of
an electron spectral index independent of the flux state. In this work, we
extend the analysis done on Mrk 421 for other two high-energy peaked BL Lacs:
Mrk 501 and 1ES 1959+650.
