Dramatically increase filter service intervals with our pre filter skins. Available in standard 40 cell (red) or 60 cell (dark grey). The 40 is more 'coarse' foam where the 60 is more 'fine'. Both will provide additional protection, the 60 will become 'plugged' sooner, however if running in fine silt/dust everyday we recommend the 60 provided it can be cleaned everyday. Multiple pre oiled units can be swapped out in minutes without removing the base filter and are cleaned much easier as well.