  We explicitly show the analogy between the symmetry breaking scheme for the
GUT flipped $SU(5)$ with that of the Weinberg-Salam theory of electroweak
interactions. This allows us to construct the embedded defect spectrum of the
theory flipped $SU(5)$. We find that the spectrum consists of twelve
gauge-equivalent unstable Lepto-quark strings, which are analogous to W-strings
in electroweak theory, and another string that is gauge inequivalent to the
Lepto-quark strings, which we call the `V-string'. The V-string is analogous to
the Z-string of electroweak theory, correspondingly admitting a stable
semilocal limit. Using data on the running coupling constants we indicate that
in the non-supersymmetric case V-strings can be stable for part of the
physically-viable parameter space. Cosmological consequences are briefly
discussed.
