TwinAir Foam Filter More than 40 years ago, the sandy and gritty soils of the Netherlands - and subsequent engine failure - proved that foam and paper filters provided airflow to drivers, but did not protect them. The breakthrough of Twin Air, the combined double-layered design combines performance and protection. The fused layers of open-pored foam and the thin inner foam capture even the smallest particles. The new rounder design increases airflow. This also applies to minimized seams, made possible by a revolutionary micro-gluing process: shorter seams = more foam = more flow. - with fluid and flame retardant foam, laminated inside the filter - washable and reusable (40 to 50 times is common) - two-layer foam (according to specification with equal and distributed cells) - grease-free sealing ring - high quality (hand assembled and checked for a perfect fit)