Melt Blown O Series Filter Cartridges features fused and intertwined polypropylene fiber without the use of chemicals or glue. The fibers are bonded randomly to form 3-D microporosity in three zones. There are fine fibers for efficient particle removal and coarse fibers for strength of the structure. Changing fiber size and density creates the needed filtration rating. With lower density on the outer surface and tighter pores when moving to the inside, it can remove contaminant effectively, such as suspended substances, particulates and rust, providing efficient filtration and long service life. The orange-peel surface texture increases the filtration surface area and dirt holding capacity.