  A growing number (over 100!) of extra-solar planets (ESPs) have been
discovered by transit photometry, and these systems are important because the
transit strongly constrains their orbital inclination and allows accurate
physical parameters for the planet to be derived, especially their radii. Their
mass-radius relation allows us to probe their internal structure. In the
present work we calculate Safronov numbers for the current sample of ESP and
compare their masses and radii to current models with the goal of obtaining
better constrains on their formation processe. Our calculation of Safronov
numbers for the current TESP sample does show 2 classes, although about 20% lie
above the formal Class I definition. These trends and recent results that argue
against a useful distinction between Safronov classes are under further
investigation. Mass-radius relations for the current sample of TESP are
inconsistent with ESP models with very large core masses (\geq 100 M\oplus).
Most TESP with radii near 1RJ are consistent with models with no core mass or
core masses of 10 M\oplus . The inflated planets, with radii \geq 1.2 RJ are
not consistent with current ESP models, but may lie along the lower end of
models for brown dwarfs. Although such models are nascent, it is important to
establish trends for the current sample of ESP, which will further the
understanding of their formation and evolution.
