KX MATRIKX 01-450-20-GREEN 1 Micron Carbon Block Filter, 4.25" x 20", Big Blue 0.6 m nominal filtration, high chemical adsorptive capacity, high voc reduction Performance tested and verified by independent laboratory testing "The chlorine taste and odor guzzler" Dimensions: 4.25" x 20" (big blue) Model no.: 01-425-125-20