Coarse open-pore foam catches airborne dirt, grime and sandFine open-pore inner foam acts as a second filter to trap the smallest particles while ensuring maximum air passageExclusively developed adhesive ensures glue seams will not break downThick, flat foam, greaseless sealing ring ensures maximum contact with your airbox, while acting as a breathable gasket for increased air passageFused outer and inner elements prevent dirt and grime from being lodged between layers, unlike Twin Air, this can be a problem with inferior two-piece designs.Trapped particles can restrict airflow. And if dirt works its way into your engine, a pinhead-sized granule will gouge your cylinder, piston and rings like a bullet