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You often hear that there is no need to reinvent the wheel, but it does seem that every other part of the bicycle is completely open for discussion. Many designers and engineers have attempted to change the basic drive train, and one of the most common solutions has been internal gearing located in the rear hub. But Polish developer Stefan Migaszewski has looked to another solution, one that puts the gearbox at the bottom bracket.
Migaszewski's solution would locate the gearbox in the bottom bracket shell, which would offer the ability to shift gears while stationary and while pedaling. This would also make it easy to go to the lowest gear at a stop, much like shifting into first gear in a car.
With three effective gears of approximately 24, 33 and 45 teeth, the efneo system as it is called would thus replace the front derailleur, but not necessarily the rear derailleur.
It is similar to Truvativ's HammerSchmidt crank, a system that offers effectively two front gears at the flick of a switch.
| Product Model | Inside Diameter | Outside Diameter | Thickness |
| 5203N NACHI | 17 | 40 | 17.5 |
| 5202AN NACHI | 15 | 35 | 15.9 |