You need the optionally available UG MB XHP (high-pass crossovers) if high-pass filtering is not available. The UG MB XLP (low-pass crossover, if low-pass filtering is not present). It may also be necessary to use the adapter cable kit UG MB SCC, this is required if there is only one standard subwoofer in your vehicle and you want to install a second subwoofer on the passenger side, the whole but not by means of the low-pass crossover (UG MB XLP) on the original radio / amplifier but with a retrofit amplifier. In this case, the UG MB SCC is needed for the audio signal feed, this must be extended independently, suitable. For the simple connection of a retrofit amplifier you need the UG MB ACC cable kit. Please ask your ETON dealer.