This is the Harmon Kardon Subwoofer amplifer for use with the NTG2.5 COMAND system. It is used in the W211 E, CLS, ML, GL and R class. In other vehicles the amp is part of the sub-woofer.
If you are retrofitting Hard Disk COMAND to a car with HK sound system you need to add this amplifier and use the appropriate retrofit harness.
** Special order, will take a few days to arrive **