Mass within and above the He II, He I, and H convection zones as a function of T_eff. The H convection zone is separate from the He I convection zone in only a few models. For stars hotter than 22 000 K, the temperature at the bottom of the convection zone is less than a factor of 2 higher than T_eff and is probably not precisely determined by interior models; it is not shown. The color code is the same as in Fig. 2.