@Lapchik On my street bike (XSR700) I went with the longest 18" stainless muffler. I wanted good tone, with minimal volume change. It worked... and I still have the "quieter core" should I want it quieter yet. I did the research contacting Delkevic to verify no ECU reflash needed and that it was under 96 dB A. It worked great except where it burns my leg! I did some exhaust wrap and a shield over it so that's solved. I don't particularly trust carbon fiber to not wallow out at the holes, fraying and breaking, so I stayed with stainless.