  The equilibrium size and temperature limits of thermally and chemically
equilibrated $e^+e^-\gamma$ plasma drops are investigated at a given energy
content. For a plasma to be equilibrated it must be opaque to electron and
photon interactions. The opaqueness condition is determined by comparing plasma
size with the mean free electron and photon paths. We calculate those paths
using thermal Lorentz-invariant reaction rates for pair production and
electron(positron) and photon scattering. The range of the corresponding plasma
temperature and size is evaluated numerically. Considering the energy and size
we find that the opaque and equilibrated plasma drop may be experimentally
attainable.
