Pentek CBC-20BB # 155312 CBC20BB 20 Inch Big Blue Replacement Carbon Block Water Filter Compatible With Culligan / Ametek / US Filter / Plymouth / Kleen Plus / American Plumber / Bruner & Many Other Brands. Big Blue Half Micron Carbon Briquette Water Filter. 20" long X 4 1/2" diameter. 6 per case, sold individually. Ametek # 155312 CBC Series cartridges are highly effective at reducing unwanted taste, odor, chlorine, certain VOC's and pesticides from potable drinking water. With a nominal 0.5-micron rating, they are equally effective at reducing Cryptosporidium and Giardia cysts, as well as fine sediment. They also make excellent polishing filters or pre-filters in applications requiring fine filtration and high capacity. This is an excellent prefilter. Order a case and save even more.