This is the pre-filter the Merlin-Garden Pro comes with. It is a 5 micron carbon block that can filter out sediment, chlorine, and other contaminants. It can not filter out dissolved minerals like calcium, magnesium, & iron. If you have high amounts of these, you may need pre-filtration for the Merlin-Garden Pro with a softener. This carbon pre-filter will give you approximately 1,500 of Reverse Osmosis water, depending on inlet water quality.