Pleatco filter cartridges are a system. This system includes CORES, MEDIA (Filtration Fabric), BANDS, and END CAPS. At Pleatco, we talk about 'Fluid Dynamics'. Pleatco does research and works with the best companies in the world to design the strongest and most efficient filters. A properly designed core MAXIMIZES the filtration area, increases flow, and creates uniform flow distribution through the entire cartridge increasing its life and the cleanliness of your water. Simple! The following parts work together to create the Pleatco Filter Cartridge.