  A family of spherical shells with varying thickness is derived by using a
simple Newtonian potential-density pair. Then, a particular isotropic form of a
metric in spherical coordinates is used to construct a General Relativistic
version of the Newtonian family of shells. The matter of these relativistic
shells presents equal azimuthal and polar pressures, while the radial pressure
is a constant times the tangential pressure. We also make a first study of
stability of both the Newtonian and relativistic families of shells.
