The K&N drop-in High-Flow air filter for the 2004 BMW 525i (2.5L inline-6) is a washable, reusable replacement engineered from layered, oiled cotton media to improve airflow while trapping contaminants. It installs into the factory air box, aims to increase horsepower and is designed for long life with K&N's no-hassle lifetime limited warranty, providing a reusable alternative to disposable filters.
K&N 04 BMW 525i 2.5L-L6 Drop In Air Filter