  We study extensions of the Standard Model with general new vector bosons. The
full Standard Model gauge symmetry is used to classify the extra vectors and
constrain their couplings. We derive the corresponding effective Lagrangian,
valid at energies lower than the mass of the extra vectors, and use it to
extract limits from electroweak precision observables, including LEP 2 data. We
consider both universal and nonuniversal couplings to fermions. We study the
interplay of several extra vectors, which can have the effect of opening new
regions in parameter space. In particular, it allows to explain the anomaly in
the bottom forward-backward asymmetry with perturbative couplings. Finally, we
analyze quantitatively the implications for the Higgs mass.
