For that added protection during those unsure moments, Injen Technology's Hydro-Shield pre-filters are race proven material manufactured from highly durable polyester. Uniform micron openings allow the filtering of debris .005” or larger. The Hydro-Shield pre-filters are factory treated using an embedded hydrophobic process, which offers consistent airflow, water repellency and maintains horsepower gains. (Please note that this item is water repellent, not water proof)