The Rotor Q-Ring Limited Black is a special limited edition, featuring a matte black look. The thought behind the Rotor Q-Ring Aero chainrings is a simple one: every pedal stroke encounters a dead point. This is where the cranks are perfectly vertical. You can't exert any meaningful power at that point, so you'll want to get past it as quickly as possible. Rotor Q-Rings have fewer teeth at this point, allowing you to get through it quicker. They then provide you with maximum gearing during the part of the pedal stroke where you can provide the most power. This theory helps you get through the dead spot quicker, meaning you loose less power when you try to reach your optimal power band. This increases your pedalling efficiency, and reduces the amount of lactic acid you produce as well as your fatigue levels.
The technology behind Rotor is all about efficiency. Rotor believes that their product might not necessarily be faster of themselves, but that they help you generate a more efficient pedalling motion, thus reducing the net time it takes you to cover a time trial for instance.
Various scientific studies have proven the positive effect of the Rotor Q-Rings by now. Maybe even better proof are the numerous victories achieved in the pro peloton using Rotor Q-Rings.