Replacement filter for the Twin Air Power Flow Kit. This Backfire filter includes a laminated layer of backire-retardant foam. Twin Air Filter's patented 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. An air filter is your engine's only protection against the elements, and your stock filter isn't up to the task. Replace it with a Twin Air- the #1 filter system proven on motocross tracks around the world. Twin Air's fused layers of open-pore foam and fine inner foam trap even the smallest particles-without restricting airflow!