Tail Light Bulb Unit Compatible With 2013 2014 2015 2016 2017 2018 Cadillac ATS XTS 3.6L Replaces 13579168 84198978. Effectively reduce the vehicle’s demand for electricity, prolonging battery life. [Easy To Install] Plug and play, only basic tools (e.g. screwdriver) are required during installation, easy design, users can complete the installation by themselves.