For your 2013 Audi Allroad you will want the Curt Powered Tail Light Converter with 4-Pole Flat Trailer Connector item # C59236. This wiring harness will provide your Audi with a 4-flat vehicle connector to control your trailer's lighting functions.
For a ball mount, I recommend the Curt Towing Starter Kit for 2" Hitches item # C45534. This towing kit will provide you with a 2" ball and a fixed ball mount with a 3/4" rise and 2" drop. It also includes a hitch pin and clip, hitch receiver... view full answer...