Koni's FSD (Frequency Select Damping) technology is now known as the Koni "special active" line of shocks and struts. The technology behind these dampers is very interesting. Valving and feedback is constantly controlled and changed by the frequency of the vibrations the shocks are experiencing from the road underneath. This gives the special active shocks a huge range of ride control. They become very soft and compliant on rough roads, and will stiffen and give a sportier feel on smooth tarmac. The perfect shock for any driving situation. Best of all, they need no manual adjustment and act just like a factory active suspension, without any wires or switches. This technology was so embraced by some auto makers that they are using it as OEM on their cars. These dampers can also be used with lowering springs down to 1.25 inches without effecting response.