[. . . ] Speaker systems that have been defining the standards of their class, again and again, and were constantly redeveloped to offer our customers the optimum in sound. [. . . ] MB QUART feels confident that you will enjoy your new Reference system. Should you have any questions about Reference or any other MB QUART products, please feel free to send us an email to info@mbquart. If you are not having the installation carried out by a specialist workshop, please read the following installation instructions carefully. Please observe the safety requirements relating to supporting chassis members, the applicable road safety regulations and the instructions of the vehicle manufacturer when installing and using the loudspeakers. Always protect your loudspeakers during installation and use against damage, spray water and overloading. Disconnect the minus terminal of the vehicle battery during installation in order to avoid possible short-circuits. [. . . ] Note: If you do not install the subwoofers and mid-range loudspeakers in the provided installation spaces of the car, rings for flush and surface mounting as well as speaker grilles are available as optional separate accessories from your specialized dealer. [. . . ]