One of the problems I found with the Calmini filter, is that there are no clear instructions for cleaning and oiling it. I asked Calmini about this and got two different answers! One guy said no oil, another said light oil, and no recommendations on how to clean it. My experience with foam filters in dirtbikes is pretty extensive, and when they get just a bit dirty, they flow like shit. The K+N is easy to clean and re oil, instructions are clear and easy to understand, and the pleated design effectivly gives the filter much more area to flow through. There's some debate on wheather the K+N lets in too many small particles, but that data is mostly biased in favor of another manufacturer's sales strategy. I've been using K+N filters in all my motorcycles for years and most of my 4 wheel vehicles too, with no adverse affects on engine wear, and only better performance to show for it, and I'm kinda picky about that.