Does anyone know if the headers from a 2011 backwards ER6N/Ninja 650 are the same diameter as the 2012 onwards? I know they made it a single piece exhaust from 2012, but the headers look the same apart from the fact they were welded to the muffler. I know the muffler was upgraded for 2014 (just a new baffle, I think), but it's still one piece and preventing me from using a slip on instead of buying a whole exhaust which I'm pretty sure also requires the power commander etc. Much easier if i could just grab a set of older headers and use a slip on but if the headers have a smaller internal diameter I'd rather not do it. Justus: Please get to know the forums before creating discussion threads. Topic does not belong in General. Try: Technical & Troubleshooting Forum.