Using this OLM rear diffuser on your 2015 - 2021 Subaru WRX or STI is super easy. First, make sure your car is clean and dry. Then, use the included installation hardware to attach the diffuser to the rear of your vehicle. You can do it yourself or get help from a friend. Just follow the basic instructions and you'll be done in no time. As for maintenance, regularly wash the diffuser with a mild car soap and a soft cloth. Avoid using harsh chemicals as they might damage the paint. Also, check the installation hardware every few months to make sure it's still tight. If you notice any signs of wear or damage, contact us right away.