Spun bonded Filter Cartridges are made of 100% polypropylene fibers, which have been carefully spun together to form a true gradient density from outer to inner surface. The superior structure remains integral even under severe operating conditions and is no media migration. Polypropylene fibers are blown continuous on central molded core, without the need for binders, resins or lubricants. Unfiltered fluid passes through depth filter matrix , enables the progressive retention of finer particles, providing high efficiency, high dirt retention & filter life. Fluid flows from outside to inside through filter media. Particulates are held securely in the filter matrix and clean fluid flows to the downstream side of cartridge. Product includes p & p if bought alone.