Twin Airs filter design, high quality materials, and superior construction deliver unbeatable performance and protection - and make Twin Air Filters the hands-down choice of more. Plato said, Necessity is the Mother of Invention. Over 30 years ago, the sandy gritty soil of the Netherlands - and the resulting engine failures - gave us that necessity. The single-foam and paper filter gave riders air flow, but failed at protection. Twin Airs breakthrough, fused-dual-layer design combined performance and protection. The fused layers of open-pore foam and fine inner foam trap even the smallest particles - without restricting airflow.