Since in particular cases the inner ring rather than the outer ring of the ball bearing should be preloaded, all “K” disc springs are designed such that the outer diameter suitable for one size of bearing will also fit the inner diameter of another size of bearing. For example, a “K” disc spring which is designed for preloading the outer ring of a size 6302 bearing, can also be used to preload the inner ring of a size 6205 or 6305.