K&N direct fit stock replacement air filters - these are the original high-flow air filters. Since 1969 K&N Engineering has been designing, manufacturing, and enhancing high-flow air filters truck, car, SUV, and motorcycle enthusiast interested in maximizing horsepower, acceleration, and fuel-efficiency. K&N not only has more applications than any other manufacturer of similar product, these guys invented the high-flow category and high-flow technology. How good is K&N? Well, they're the only air filter used at the Indianapolis 500. The K&N FilterCharger air filter is designed to achieve high, virtually unrestricted air flow while maintaining filtration levels critical to ensure long engine life. A K&N filter directly replaces the factory filter, making for a quick and easy install. K&N air filters are constructed using 4 to 6 layers of cotton gauze, which is between two epoxy-coated aluminum wire screens.