The WGB21B is a great "point of entry" filtration system and an excellent alternative to the larger WGB22B for smaller homes. The WGB21B will filter water directly from your source. This means that water from every outlet will have passed through this filter, providing up to 50,000 Gal. of clean water for the entire family. The first stage of this system houses a 5-micron high-capacity polypropylene sediment filter (FP15B). This filter is responsible for removing dirt, rust, and most suspended solids, to protect the CTO carbon block filter. The second stage houses the 5-micron CTO coconut shell carbon block filter (FC15B). Block carbon is more effective than other forms of carbon in that it is finely ground up carbon packed into a solidified block. This means they have a higher density than other types of carbon filters and are therefore more effective in removing their targeted contaminants. The carbon block filter knocks out bad tastes and odors, removes over 90% of sediment and chlorine, and is highly effective on chemicals, like pesticides, herbicides, and industrial chemicals.