The Selex (SX) cartridge filter (Figure 1) is a high precision graded density cartridge constructed of 100% pure polypropylene. Selex provides a very high particle retention efficiency that equates the performance of absolute rated filters. The patented Selex manufacturing process controls the density and fiber size, which are key to the filter’s performance and long life. Selex cartridge filters have sharp efficiency cutoff, fast rinse up for exceptional purity, and continuous, weld free lengths up to 40 inches (101.6 cm).