Tannins are organic matter that cause a yellow to dark tea color in water and may impart taste and odor. This effect is caused by a variety of humic and fulvic organic acids which are found in waters influenced by rainfall and runoff from natural soil and peats into streams, rivers, and lakes. Tannins have also been found in deep groundwater wells. Tannin structure varies from location to location, depending on the vegetation in the area. While not not a health issue, the presence of tannins is aesthetically displeasing. Aries Taste & Color Correction Cartridges use ResinTech® SBACR anion exchange resin to remove tannins and other organics and improve the color taste and odor of drinking water. These high capacity cartridges are sized to fit standard Slim and BB housings.