Twin Air Factory Pre-Oiled filters have been available only to our top professional race teams and OEM customers. The results have been so good that we now offer the same factory treatment to everybody. We start with an Original Dual-Stage Air Filter and completely submerge it in BIO Liquid Power Filter Oil. After the filter is massaged to ensure all pores are evenly coated with oil, it's placed in a temperature controlled room to allow the oil to completely cure. You just open the reasalable bag and install.