The Pentair Pentek R50-BB is a 10-inch pleated cartridge made from a durable, non-woven, reusable polyester fabric, at a nominal 50 micron rating. It reduces dirt, sand, silt, and rust to send cleaner water to every tap and help protect appliances and downstream filters. The media is pleated around a polypropylene core for added strength, and the Big Blue version holds more than 16 square feet of polyester fabric to maximize dirt-holding capacity and extend the time between changes. The overlap seam is sonically welded to reduce internal bypass, which improves filtration efficiency, and the cartridge can be rinsed and reused to extend its service life. It is rated for water up to 125 degrees F. The 10" x 4.5" cartridge fits Pentair Pentek Big Blue and other heavy duty housings and replaces most 10-inch pleated or sediment cartridges, with a low pressure drop under 1 psi at 10 gpm. Rinse or replace when you notice a drop in water pressure or water quality. This listing is a Pack of 8.