FACTORY FATTY: Reminiscent of the works or cone pipe once used by Factory Teams. It shares many of the same characteristics with its craftsmanship and material quality. The Factory Fatty broadens and smoothes out the power curve while boosting gains throughout the entire power band, more low-end, more mid, and increased over-rev. No matter what type of riding you do, the Factory Fatty has the benefits youre looking for. Lighter 20 gauge steel used for the body of the pipe 19 Gauge steel used for the header portion Includes O-rings on most models Hand pounded seams for smooth flow transitions O-Rings included Fits: Yamaha YZ250 1999-2021