Twin Air Pre oiled air filter Coarse, open-pore 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 cleaning, even with harsh solvents or gasoline Slightly smaller than stock filters to increase air space around the filter and improve circulation Fused outer and inner elements prevent dirt and grime from being lodged between layers. Unlike Twin Air, this can be a problem with inferior 2-piece designs. Trapped particles can restrict airflow, and dirt works its way into your engine, a pinhead-sized granule will gouge your cylinder, piston and rings Thick, flat foam, greaseless sealing ring ensures maximum contact with your airbox, while acting as a breathable gasket for increased air passage