With regard to the drive units, the mega yachts may be most closely compared to fast ferries. For the most part, fast-running, highly powered, but lightweight diesel engines are employed. The drives, usually diesel-mechanical, drive jets or propellers via lightweight reduction gears. The requirements for comfort are even higher; a special elastic mounting system (e.g. elastic engine as well as gearbox mounting) ensures maximum noise attenuation. This and certain specifics of shipbuilding require the use of specially adapted, high misalignment and structure-borne noise reducing couplings between the main engine and gearbox, as well as at the gearbox output to the propeller shaft.