This is the AUX input adapter XA-300 for Sony head units with Unilink. This unit adds two AUX inputs and a USB port*. This unit also has one Unilink input, so you can still connect CD changers, etc., that were originally connected to the head unit. *Although there is a USB port, it is not for playing USB memory, etc., but for USB audio. I connected it to a Windows 11 PC, and it seems to be recognized as an external DAC, allowing audio output from YouTube, etc., through the head unit. I have confirmed the operation with MDX-C5100. Please be sure to check if your head unit is compatible! I will upload a few photos of the operation check. Included accessories are a bus code (approx. 5m) and an RCA cable (third-party product). For more information about the product, you can download the manual from the Sony website. Please check it there for details. 250901-hk