1996 - 2005 Mk3 and Mk4 2.0L cars changed to a single valve spring design, rather than the established dual spring setup. Most likely done to reduce valvetrain drag, it limits your ability to run performance cams without additional upgrades. Therefore, when upgrading the cam, we recommend upgrading to SportTuned valve springs as well. Upper spring retainers must also change, and lower seats added. Why not upgrade to Ti retainers at the same time? Valve springs manufactured from valvetrain juggernaut Schrick in Germany.