Contraction of CoRoT-2b compared to its measured radius and inferred age. Our fiducial model has an initial radius R_ini = 2 R_J, mass M_p = 3.5 M_J, and equivalent helium mass-mixing ratio Y = 0.30. The evolution for models with different initial radii R_ini (3 to 6 R_J), different masses (3.3 to 3.7 M_J), or a different value of Y (0.25) are shown as labeled.