I installed my Kartboy SS today, and I took pictures of both the stock shifter and the Kartboy (with the measuring tape for a scale), and put them together in this picture for anyone who wants to see the difference in size...they're pretty much to the same scale, so the difference is about the same as it is in real life.
Anyone with a B&M or a TWM shifter is definitely welcome to add to this picture so we can get an accurate, to-scale idea of the size differences between all of the choices.

Anyone with a B&M or a TWM shifter is definitely welcome to add to this picture so we can get an accurate, to-scale idea of the size differences between all of the choices.
