Twin Air Filter's design, high quality materials and superior construction deliver unbeatable performance and protection - and make Twin Air Filters the hands-down choice of more World & National Champions than all other filters combined.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 ensures glue seams will not break down.Thick, flat foam, greaseless sealing ring ensures maximum contact with your airbox, while acting as a breathable gasket for increased air passage.Fused 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 it's way into your engine, a pinhead-sized granule will gouge your cylinder, piston and rings like a bullet.Used Pre-Oiled Air Filter. The coarse outer Shell catches airborne dirt, grime and sand. The fine inner layer traps the little stuff (click to enlarge).Twin Air filters are designed to increase airflow while ensuring the highest level of protection from dirt/dust.