This is a Nicestuff 69300 (which is similar to the Nicestuff 68300 or NSD68300 or PR300 or 68300-PAC EasyMute Premium) handsfree integration harness for use withselect Audi and Mercedes vehicles with ISO radio connectors and premium audio systems with an external amplifier (ex: BOSE, JBL, Harmon-Kardon, Infinity, etc.). This kit features a soft-mute switching relay that sits on the line-level signal between the radio and the amplifier to provide a clean swithcing of the radio audio to the handsfree audio. Compatible vehicles include: 1995-2000 Audi A4/S4/RS4 WITH BOSE 1994-2000 Audi A6 WITH BOSE 1993-2000 Audi A8 WITH BOSE 1999-2000 Audi TT WITH BOSE 1993-2003 Mercedes C-CLASS WITH ACTIVE SOUND SYSTEM 1996-2006 Mercedes CL WITH ACTIVE SOUND SYSTEM 1997-2004 Mercedes CLK WITH ACTIVE SOUND SYSTEM 1996-2002 Mercedes E-CLASS WITH ACTIVE SOUND SYSTEM 1997-2005 Mercedes M-Class W163 WITH ACTIVE SOUND SYSTEM 2000-2002 Mercedes S-CLASS WITH ACTIVE SOUND SYSTEM 1993-2001 Mercedes SL WITH ACTIVE SOUND SYSTEM On activation of the Mute line, the audio will switchover to the handsfree kit. You can also use this harness to integrate audio into your car stereo from other mono sources by triggering the mute enable line (navigation units, radar detectors, CB radios, etc.). A carkit-specific adapter harness may be required for your installation (I have some of these in my booth), or the connections can be made individually. Available on the connection to the carkit is: VBATT - constant +12V power supply Ground - chassis ground Ignition - switched +12V signal Mute - active-low trigger Mute connection Speaker (+) - differential mono audio signal from the carkit or device Speaker (-) - differential mono audio signal from the carkit or device As this harness features ISO connectors, it can be used in combination with Parrot2Car or ISO2CAR vehicle-specific adapters from various suppliers to adapt a bluetooth carkit to certain additional vehicles with factory amplified/premium audio systems. I have a mobile electronics installation business and am selling off some excess inventory. Please feel free to send a message if you have further questions about any of my items. Thanks for looking!