Coarse, open pore outer foam catches airborne dirt, grime and sand Fine open pore inner foam acts as a second filter to trap the smallest particles while ensuring maximum air passage Exclusively formulated adhesive withstands repeated cleanings, even with harsh solvents or gasoline Slightly smaller than stock filter to increase the air space around the filter and improve circulation Fused outer and inner elements prevent dirt and grime from being lodged between layers, this can be a problem with inferior 2-piece designs. Trapped particles restrict air flow, and if dirt works its way into your engine, a pinhead sized granule can gouge your cylinder, piston and rings like a bullet Thick flat foam, greaseless sealing ring ensures maximum contact with your airbox, while acting as a breathable gasket for increased air passage