Not useful. I've been trying for years to get rid of the useless Firefox scrollbar, which I never use, because it is too thin to try and click on it. I thought this add-on would allow me to finally do so. However, as clearly stated by the add-on when you try to change the scrollbar width, this is not allowed by Firefox. You can only change the scrollbar colors, but I don't know why anyone would want to do this