FMF 2 Stroke - Expansion ChambersFATTY PIPE: With well over 35 years of racing experience behind it, the Fatty Series pipe delivers race proven performance. The 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 Fatty has the benefits youre looking for. More tractable power, improved throttle control Provides power gains throughout entire power