This carbon fiber gurney flap is a great addition to your 2015 - 2021 Subaru WRX/STI. To use it, first clean the mounting surface of your STI spoiler really well. You can then apply the flap using the 3M double - sided adhesive. Make sure to do the installation in a warm place, about 70 degrees Fahrenheit, as it will make the adhesive work better. When it comes to maintenance, just clean it with a gentle car cleaner from time to time. Avoid using harsh chemicals that could damage the carbon fiber finish. That way, your gurney flap will keep looking great for a long time.