Since the end of last year, Fiat has been mass-producing the first fully variable valve train, which is based on electro-hydraulic valve phasing [1]. The Schaeffler Group secured the rights to UniAir technology at an early stage and, as a development partner for the system and its key components, describes the main design steps in this report. Ensuring reliable operation and absolute precision for the system even at very low temperatures and over the entire lifetime — with each solenoid valve carrying out at least 330 million switching operations — was a major challenge.