Sometimes the reason to upgrade the shift knob at the end of a car’s or motorcycle’s gear stick stems from the need to replace an old broken part with a new authentic one. Other times, though, the objective is to customize. In general, these replacement parts need to put function first, since one’s hand must be able to grab the knob firmly in order to move the stick from gear to gear. But some people will risk shift knobs shaped liked skulls, dice, or even Rat Fink in a desire to be cool. More common are rounded custom knobs made of eight balls, palm-size marbles, or clear acrylic, encasing everything from toys to bullets safely inside.