This filter features three layers of oil-free synthetic media and requires no oil during maintenance to provide maximum convenience. Its progressive layering provides great filtration efficiency and dust holding capacity. This media is best suited for trail riding and mudding in damp environments. Pro DRY S filters are easily recharged with aFe's POWER CLEANER. aFe POWER performance air filters use a rounded, evenly spaced pleat design which allows for more usable filter surface area, providing increased flow and greater dust holding capacity. Its surrounded by expanded metal that provides additional protection, preventing filter collapse and direct impact. This aFe POWER performance air filter is constructed with a polyurethane base and top. Unlike other materials that degrade after repeated heat cycles in an engine bay, polyurethane maintains its original molded shape. Just like our air filters, this 1/2” open cell polyurethane foam Pre-Filter (PN 28-20004) is washable and reusable. Just simply tap to remove excess debris between your usual cleanings, and then wash it with aFe POWER Cleaner when you service your air filter. Pre-Filters provide added piece of mind for those who operate their vehicle in dirty environments. This foam pre-filter captures large particles before they reach the air filter – increasing efficiency and dust holding capacity, without negatively affecting airflow. For even further protection, it can be oiled with aFe’s air filter oil.