EVOPS Polaris RZR 1000 V-Flow High Performance Air Filter System is a Direct-Fit Replacement air filter for the RZR 1000 models and fits in the factory air box. Our higher flowing air filters offer significant improvements in air flow, filtration and adds about 2 HP while being washable and reusable. We start with multiple layers of cotton gauze combined with our synthetic filter media resulting in a superior filtration system. Our air filters trap the smallest dirt particles that ordinary cotton-gauze performance filters can t capture. This product includes our custom Pre Filter which is designed to keep out particles of dirt and sand debris as small as .005?. Our Pre-filters are run dry meaning no oils or additives are required so there is no dirt sticking to the main filter resulting in loss of airflow and horsepower. Additionally, our Pre-filters add a second level of protection. The woven mesh is specially treated using a proprietary process to repel water. This hydrophobic water repellent process is not sprayed on; consequently there is no airflow loss. Our Pre-filters are used and recommended by top professional engine builders and race teams worldwide.