I couldn't stand how quiet the stock exhaust is on the Ninja 250 so I ordered one of these $65 exhaust on Ebay. I wasn't too sure what to expect on the quality and sound but after taking 10 minutes to install (direct fit), I was pretty impressed (so far) that I even made a video out of it lol.
https://youtu.be/rXbzVE9XpRg