I have a PC spark arrestor. But definately keep on the FMF PC when I'm on private land. I just don't like teh idea of restriction. And yes, I have seen fires start by sparks. The carbon in the pipe gets hot, comes apart and blows out the rear red hot. I saw it come out of my cusins bike, hit the ground and catch some leaves on fire. Thankfully I saw it. We had a ban on outdoor fires here in NC a few years back due to a major drout. It was a close call.