FlowFilt Polypropylene pleated filter cartridges have been designed as an effective membrane prefilters and as final polishing filters for many liquid processing applications. The cartridges are double layered filters. The graded porosity design removes particles in sequence such as larger particles by the more open outer layers and the smaller particles by the tighter inner layers. The outer layer acts as the prefilter while the inner layers provide the rating at the specified pore size. This efficiently spreads the contaminants throughout the media matrix resulting in superior contaminant holding capacity, lifetime & pressure drop as compared to other media cartridges.