THUNDERHEADER 2017-2023 Harley-Davidson FLH X-Series Our X-SERIES™ Exhaust is our newest line in creating maximum horsepower. With our 2" headpipe, equal length tubes, and a larger collector, this exhaust is made specifically for Harley-Davidson's Milwaukee-Eight™ engine. Includes full coverage heat shields. 18mm and 12mm O2 sensor ports. ***NEW IN BOX***
