The can on my 06 525 exc looked horrible (scratched and tarnished) and the end cap had been modified and sparky removed. Created quite the "tumble" effect in the end section of the can. Had plenty of bottom end but would not rev out at all. Just went flat on the big end. I already jetted it up which helped some but still wouldn't even get close to approaching the rev limiter. Not that I want to bounce off the limiter but when I tried to open it up on the straights, I had to short shift it to keep it climbing in speed. So on a whim (couldn't find hard proof), I picked up a 2012 450 sx-f can off of flea bay for cheap with free shipping. I msg the seller and got some "rough" dimensions but I lucked out. It bolted right up. Fit tighter on the header pipe than the factory can but I'm guessing the original was just whooped from being so old. Bike will pull the to the limiter no problem now and never goes flat on top. Very quiet idle and cruise but if I get into the throttle aggressively under load, its quite a bit louder but not obnoxious loud. Just need to add a sparky and I'm all set. Just an FYI for others out there with older EXC that don't want to drop a lotta cash on a slip on. I payed $80 free shipping.