This part is a direct plug in OEM add-on that gives a USB connection for the AUX input on the car. It installs inside of the center console and behind the factory head unit. I bought it and used it on my wife's legacy to allow here to use an iPhone with the lightning cable to work with the aux function. Our 2011 legacy did not have bluetooth and the lightning to aux adapter cables never worked.
Once installed you can plug you phone into a lightning usb cable and use the aux function on the car. Steering controls work with it.
Part number SPN0000970. You can find install instructions via google or PM me and I can email them.
Make an offer, it's collecting dust.