Unique patented hub engagement mechanism – VRT (Vortex Ring Technology). Reliable and an instant with just 6 degree lock-in, which is also easy to service, how to combine all these qualities together in a hub? VRT makes it all possible. Its progressive lock-in makes engagement stronger the harder you pedal. You get reliable torque transfer under any conditions! 60 engagement points, which are all lock at once, switch instantly into a drive mode. Yet with its two cylinders design, it is easy to service with no specific skills required.