The RCV drive shaft works according to the principle of drive shaft used on full scale vehicles. It is specifically miniaturized to be integrated into RC models.
This is the object of the patent N° : FR 12 59048.
The balls driveshaft «RCV» keep velocities in each angular position of driveshaft.
It's an advantageous alternative to "double joint". The very high level of accuracy and durability offers no play and no wear run after run.