It is important to measure for exact fit. We had to "customize" our stairs during my install process. Which is ok, as my wife has been asking me to upgrade the stairs to hardwood anyway.
Here is my YouTube video of our Lippert Solid Step install. We even removed our Torklift GlowSteps (not factory) to install the Lippert steps.
https://youtu.be/Ga8a6Ox3v3A