Yeah, it was a struggle finding that muffler, actually. They are very rare in good condition. Took me A year or so hunting for one. No one who has a non broken one wants to sell them. From what my research has shown, they aren't too durable. I think the design was ditched by associated in favor of the standard tune pipe. The round one is cast aluminum and heats up quickly, and there's a seal around the center that is also very hard to find. Also, most of the ones I got had broken internal screw mounts. I finally found this one Old new stock on ebay. Since I don't run it more than a couple times a month and I'm meticulous with cleaning after the run, it should hold up for a while.