Omni Corporation CB1 Carbon Block Undersink Replacement Cartridge Micron Rating - 0.5 Dimensions - 2 5/8 inches x 9 3/4 inches Flow Rate - 1.0 Gallons per minute NSF 53 certified for Cyst reduction Filter Life - 1,000 Gallons or 12 months NSF 42 certified for the reduction of Chlorine Taste and Odor and Nominal Particulate Reduction Class I