AIRAID Premium Filters are constructed using the finest materials available today. All AIRAID Premium Filters utilize a urethane body that won't crack or curl like our competitors' rubber units. Filtration is second to none with the combination of our proprietary SynthaFlow and multiple cotton gauze layers. All AIRAID Premium Filters are 100% reusable and feature a Lifetime Guarantee. We test to SAE standard J726, the method for testing fractional efficiency of a filter. We could say that we capture 99.997 percent of particles of 10 microns and larger, most air filters, and capture the full range of particulates, even down to 2 microns. Our filters are so efficient that we test all the way down to 0.3 microns. At 2 microns, our filters capture almost twice the percentage of particulates that our competitors do, and more than 6 times the amount at 0.5 microns.