Air Filter. The Twin Air 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 and National Champions than all other filters combined. 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. Twin Air filters are designed to increase airflow while ensuring the highest level of protection from dirt / dust. 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.