K&N Pre-Filter Rain Sock For 4 Air Filter Specially designed filter wrap made to extend the service interval of a 4 round K&N air filter when used in severe dusty or wet conditions. Made from durable polyester material containing uniform micron openings that will stop small dirt and water particles yet adds little restriction to airflow. Features: Double stitch elastic opening 4 Diameter x 2.25 Tall Washable with K&N filter cleaner Made in the USA