Pentair Pentek R Series Cartridges are manufactured from a durable, non-woven and reusable polyester fabric that is suitable for a wide range of filtration uses. The media is pleated around a polypropylene core for added strength. The pleated end caps of the standard cartridges are immersed in a thermo-setting vinyl plastisol. The Big Blue cartridges have a molded end cap with gaskets. The pleated ends are sealed to the end cap with a thermoplastic adhesive.