The WGB21B is a great "point of entry" filtration system and an excellent alternative to the larger WGB22B (4.5"X20") for smaller homes or where limited space may be a concern. The WGB21B will filter water directly from your source. The first stage of this system houses a 5-micron high-capacity polypropylene sediment filter (FP15B). This filter is responsible for removing dirt, rustand most suspended solids, to protect and extend the life of 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. The carbon block filter knocks out bad tastes and odors, removes over 90% of sediment and chlorineand is highly effective on organic chemicals (VOCs) like pesticides, herbicidesand industrial chemicals. The WGB21B filtration system will remove these tastes and odors.