A new, perfectly oiled ProFilter Air Filter provides maximum airflow and increased horsepower. Ready-to-Use Air Filters are constructed of dual-layer, reticulated foam. Reticulation is a process that opens up the foam cells, allowing for increased air flow and horsepower. The dual foam layers differ in foam pore size – the innermost foam consists of a denser foam to catch fine particles of sand and powder, whereas the outermost foam is constructed of a more open pore matrix allowing for filtration of larger micron dirt particles.