This is a post-carbon inline GAC, and it's superior performing 2" x 10" inline GAC (granular activated carbon) filter that comes in the fitting size 1/4" and 3/8". Choose what style above of connector. Very simple installation. Removes smells, tastes, and chlorine from your water. Can be used with a multitude of applications including RO systems, icemakers, dispensers, and many others. Should be replaced every year. NSF certification.