  A remarkably precise observational relation for pulse core component widths
of radio pulsars is used to derive stringent limits on pulsar radii, strongly
indicating that pulsars are strange stars rather than neutron stars. This is
achieved by inclusion of general relativistic effects due to the pulsar mass on
the size of the emission region needed to explain the observed pulse widths,
which constrain the pulsar masses to be less than 2.5 Solar masses and radii to
be smaller than 10.5 km.
