The concept behind class templates is simple; they are templates which are also classes. Unlike racial progressions, savage progressions and progressive templates however, class templates utilize the HD-advancement mechanic that is used in order to advance monsters, in order to end up with a number of blank Hit Dice that is comparable to the total effective Level Adjustment or Challenge Rating. This way, the total power of the template component of a class template will be controlled, and backed up by the appropriate amount of Hit Dice. Because of this, class templates have the same Hit Dice to challenge rating ratio as player character classes.