The Omnipure CSM5621 is a replacement 5 Micron Carbon Block Filter designed to be compatible with 3M manufactured SQC filters for Water Factory/CUNO (now 3M) and for older Ionics Reverse Osmosis systems. The CSM5621 carbon block filter improves taste and odor, reduces chlorine in your water, and reduces sediment particles up to 5 microns. The CSM5621 is a replacement for the 47-9298G2. In 3 stage systems its often used as a post filter and in 4 stage systems its often used as a prefilter.