I put Rush slip-on mufflers on my 2009 FXDF. Started with 2.0 inch baffles. They were PLENTY loud. In fact, too loud for me. Since Rush supports interchangeable baffles, I then ordered 1.50 baffles, stuck them in, and have been happy since. As you get used to them, they seem to get quieter (which is just in your mind -- in actuality, if they change at all, they get louder). I doubt I'd ever re-install the 2.0 inch baffles, but sometimes I wonder what the 1.75 inch would sound like. Either way, the performance improvement is undeniable. Very satisfying power boost, coupled with Stage 1 air upgrade and mapping download.