Doulton W9221000 Imperial SuperSterasyl OBE Ceramic Filter The W9221000 Imperial SuperSterasyl OBE Ceramic Filter has all the features of the Imperial Sterasyl plusChlorine reductionandOrganics reduction The Doulton W9221000 OBE Filter has a Sterasyl ceramic outer shell with aGACcore This Ceramic Filter is aself-sterilizingfilter that can be re-used over and over again to provide absolute micron filtration down to .9 microns