Vertigo Air Filter Twin Air Vertical R2/R3 Nitro OILEDOver 50 years ago, the sandy, gritty soil of The Netherlands and the resulting engine failures proved that single foam and paper filters gave riders air flow, but failed at protection. Twin Airs breakthrough, fused dual layer design (now widely copied) combined performance and protection. The fused layers of open pore foam and fine inner foam trap even the smallest particles. The new, rounder design boosts airflow. So do the minimized seams made