Doulton-W9121021 SuperCarb 10" Ceramic Filter Candleer Candle The Doulton W9121021 Ceramic Filter has a Sterasyl ceramic outer shell with acarbon blockcore This is aself-sterilizingfilter that can be re-used over and over again to provide absolute micron filtration down to .9 microns This is athree stage cartridgecombining the highly efficient properties of ceramic with the enhanced water treatment properties of activated carbon