The Koni FSD front shock absorber is the first shock absorber to offer superior road holding without comprimising comfort. FSD stands for Frequency Selective Damping. This new technique combines the benefits of both type of ride characteristics in one perfect shock absorber.This smart suspension system adjusts automatically to road conditions as well as driving style, and in a fraction of a second. Firm for sporty driving on even road surfaces and comfortable for a smooth ride on uneven road surfaces. FSD guarantees greater stability, greater control and thus greater driving pleasure.They are not suitable for use with aftermarket sports lowering springs.