This
Reef Master Filter Cartridge twin pack is intended to replace the filter fleece cartridges in the final stage of water filtration.
The pack contains two replacement filters, that have a bayonet fitting, covered in dense, fine filter fleece. These are ideal for water filtration, and final polishing before the water is returned to the tank. The filters are also designed to prevent bubbles from travelling into the main tank.
Please refer to the Spare Parts Manual for more information.