  Spherically symmetric classical model of an elementary particle or a black
hole spacetime without central singularity had been constructed by O. B.
Zaslavskii in PRD 70(2004)104017. In this model an extremal Reissner-Nordstr%
\"{o}m (RN) black hole and a Bertotti-Robinson (BR) spacetime are glued at the
horizon such that the inner/core spacetime is the regular BR while outside is
the extremal RN. In this note we investigate the stability of such a particle /
regular black hole against linear radial perturbations. The model turns out to
be stable against such perturbations with a linear equation of state after the
perturbation.
