Using this K&N air filter is easy. First, locate the air filter housing on your Honda TRX400EX or TRX400X. Open the housing and remove the old filter. Then, place the new K&N filter in its place and close the housing securely. When riding in dirty and dusty conditions, check the filter regularly. If it looks dirty, it's time to clean it. To clean, use a K&N filter cleaning kit. Gently wash the filter with the provided cleaner, rinse it thoroughly, and let it dry completely. Once dry, re - oil the filter according to the instructions on the oil bottle. Avoid using harsh chemicals or rough brushes on the filter, as this can damage it. And remember, with this filter, you usually don't need to change the jets, but if you notice any performance issues, it's a good idea to consult a professional.