Captures a wide variety of airborne allergens including dust, mold, pet dander, and dust mites. Rugged and durable. Will not warp or leak under normal operating conditions. Up to 8-times more effective at capturing micro particles than ordinary fiberglass filters. Excellent for high-velocity systems and maximum air flow. Lasts longer compared to a basic fiberglass filter which is supposed to be replaced every month. This product is listed and rated by Underwriters Laboratories as U.L. Class 2.