Katadyn Pocket Replacement Element CeramicThank you for your support of small businesses like Highwater Filters. Replacement Cartridge for the Pocket Filter by Katadyn. The tried and tested ceramic depth filter Katadyn Pocket removes bacteria, protozoa and other disease causing agents. The microorganisms cannot pass through the pores of the filter ceramic (0. 2 microns) because of their size (greater than 0. 2 microns = 0. 0002 mm). Unlike disposable filters, the ceramic can be cleaned