What is theoretical travel distance?
When a key is pressed on an MX switch, the standard travel distance of the key press is roughly 4mm. Switches with shorter travel distances are often referred to as “Long pole” switches due to how the longer stem pole tends to cause the switch to bottom out sooner than a normal MX switch. This often causes a louder and more pronounced sound compared to standard MX switches, however results are not entirely concrete.
When swapping out stems it is possible to hypothesize the difference in travel distance without using any switch testing tools; however, not all switches bottom out by hitting the bottom of the switch. Cherry MX switches for an example bottom out on the side sliders, instead of the bottom pole.