There's only one Core Max. Are you asking for the difference between Ab Hits and Core Max? If so, Ab Hits is a compilation of Cathe's older workouts, and most of them are very traditional -- done on the floor without any equipment -- and combined with plank work. Core Max has newer ways of working the core (not just the abs) and is composed of 3 segments -- the first requires no equipment and incorporates a lot of traditional ab work and planks; the second has a lot of stability ball work; and the third has exercises needing a stability ball and a medicine ball (I use a db in place of a med ball). All segments work the lower back before working the abs. Core Max also has three great premixes. I have both Ab Hits and CM, and I alternate between the two DVD's. Hope this helps.
Pinky