Aprilia RSV4-R Sachs Forks 2011-2017 Mupo Fork Cartridge Kit K911 Ø25mm PistonsREF#C05APR020 *Fits only RSV4 R APRCA with Sachs forks 2011 2017* This new cartridge has been developed thanks to the experience acquired during the races supported by us. This cartridge has a K911 system. it' s a new mechanic system that allows varying the spring elastic constant in the fork without physical replacement of the spring. The difference between the other similar cartridge (C06) is the pistons diameters 25 mm instead 30 mm. Thi kind of