the mp3 knob fits ONLY two shifters - the one in the mp3 and the one in the sport automatic proteges. the thread pitch is the same however for the protege, mazdaspeed protege, protege5, mazda6, mazda3, and japanese five speed mazda rx-8.
all of the short shifters have the same thread pitch as the above listed cars as well, so the mp3 knob will not fit an aftermarket protege short shifter.