At last there's a solution that reduces vibration and improves acceleration. When your bike hits freeway speeds, simply shift into 6th gear and lower the cruising RPM. Freeway cruising becomes more enjoyable with reduced vibration, increased gas mileage while keeping the engine in the heart of its torque band. This 6-speed transmission is complete, and ready-to-install. Allows you to get about 5 mph more in the 1st gear, and around 450 rpms lower at the highway speeds. Fits Harley Davidson Softail frames and custom application. Can easily be used for 2000 and up Twin Cam 6-speed conversion..