SP Concepts Big Bore Pro Flo 2-Into-1 Exhaust For Harley Low Rider ST / Sport Glide Building on the success of the original Big Bore system, the SP Concepts Pro Flo Chambers enhance torque and horsepower through optimized reversion and expansion. Designed for riders chasing every ounce of performance, these pipes not only deliver measurable gains but also a bold, unmistakable look that turns heads everywhere you ride. Features: 4 1/2 rolled cone muffler offers increased flow for high performance applications Designed to work with properly tuned high performance motors from 88 to 143 Stepped 2 1/4 to 2 1/2 baffle for increased mid-range torque .065 stainless headers step from 1 3/4 to 1 7/8 to 2 at the collector TIG welded by hand from top to bottom Machined stainless header collars 18mm O2 bungs with 12mm adapters for performance and stock O2 sensors Includes all hardware and brackets Heat shields available separately Available in a variety of finishes: Stainless, Polished Stainless, Black and Black Onyx Note: This pipe should not be installed without a fuel tuner. This pipe is designed specifically for high performance applications and is not recommended for stock motors.