its able to move in and out freely cause the inner part is not a joint it is a hub the axel shaft goes into it with teether,it is made that way cause your car has to adjust((bumps,Uturns steering))so it slides in and out the outter part is cvjoint it is a joint for makeing left/right turns.the clips in made larger to hold the axel into the hole the semi expand to keep itinto place it must be forced in and when it pops out it can not go back in cause the cvjoint moves around and the shaft still slides in and out so there is no force to push back in the axel