Using these side splitter winglets is a breeze. First, make sure you have the Flow Design VA WRX/STI side skirt splitters (sold separately) installed on your 2015 - 2021 Subaru WRX or STI. Since all parts are pre - drilled, simply bolt the winglets onto the threaded brass fittings of the side skirt splitters. You can adjust the winglets to any position between 0mm and 20mm according to your preference and your car's configuration. When it comes to maintenance, use a mild soap and water solution to clean the textured ABS plastic. Avoid using abrasive cleaners as they can scratch the surface. And that's it! Enjoy your customized ride.