There two fundamental categories of disposable cartridges. These are surface filters and depth filters. Each exploits fundamental filtration mechanisms in different ways to target contaminants. Surface filters use direct interception to capture rigid solid particles on their surfaces and build a filter cake that helps improve filtration over time. Depth filters use all three filtration mechanisms to trap and retain rigid and semi-solids particles when there is a broad particle size distribution that maximizes utilization of its many layers. Understanding this basic concept and the contaminants to be targeted prior to selecting a filter cartridge will improve the odds that the filter will produce the desired results efficiently. Know filters and let the contaminant dictate the type you use.