Enfig SRWH-AUD3-B

-Will allow your steering wheel controls to control your new radio with the purchase of a SWCL http://enfigcarstereo.com/ENFIG_SWCL.html
-Your car handles Ignintion, illumination, reverse, parking brake and Vehicle speed sense through a computer signal called can bus.  The black box reads the can and gives you these 5 wires not found behind the radio.  Reverse and parking brake wires only work on some 2005.5 and up vehicles.
-If you are using the audi factory amp use Enfig SRWH-AUD3-HILO http://enfigcarstereo.com/ENFIG_SRWH_AUD3_HILO.html
-Does not fix low rear audio. Should only be used if you are replaceing the factory amp or do not care that your rear speakers and subwoofer are half the volume of the front. The audi radio has an ouput that is about double a standard high end radio with 4V rca low level outputs.  Our HILO harneses fix this issue.  On cars that don't say Bose on the door your rear speakers and subwoofer will be half the volume becasue the front speakers are powered by the radio..  On Audi's that say Bose on the door all the speakers will be half the volume becase all the speakers on the car are amplified.  Do a google search for "audi low rear audio" for more information.