Listing is for 12 filters. Engineered using patented carbon extrusion techniques to create 1 micron nominal block, the CB1-10 provides a genuine balance between chlorine absorption and dirt loading. To maximize the life of this cartridge, pre-filtration is recommended when the inlet water quality is either unknown or contains high volumes of 1 micron or larger particulate. Pentek is the largest brand in the filtration industry Pentek is the originator of carbon block production technology Pentek is the largest producer of carbon blocks worldwide Carbon Block Cartridge Removes Chlorine, Taste & Odor 1 Micron Filtration Fits Standard 10" Housings