Hydronix CB-45-1001 NSF Carbon Block Filter 4.5" OD X 9 7/8" Length, 1 Micron Carbon block filter for a water filtration system 4.5" OD and an overall length of 9-7/8" Coconut shell carbon filter media with polypropylene outer/inner wrap, end caps and netting Particle retention size of 1 micron Meets ANSI/NSF Standard 42 certification for material requirements only