Why use a foam air filter? Pipercross air filters consistently outperform paper and cotton-gauze rivals to supply air to the engine - even when dirty! This is thanks to the multilaminate construction used in every Pipercross performance air filter. Layers of varying porosity foam all work together to trap different sized particles. Race Specification Air Filters Unique to Pipercross, we offer a range of race use only motorcycle air filters with a specification designed to maximise airflow and performance. Fuelling modifications are necessary to take advantage of the increased airflow and to prevent damage to the engine.