  Vector-like quarks are a common feature of "composite" Higgs models, where
they intervene in cutting off the top-loop contribution to the Higgs boson mass
and may, at the same time, affect the Electroweak Precision Tests (EWPT). A
model based on SO(5)/SO(4) is here analyzed. In a specific non minimal version,
vector-like quarks of mass as low as 300-500 GeV are allowed in a thin region
of its parameter space. Other models fail to be consistent with the EWPT.
