Water picks up dissolved minerals like calcium and magnesium easily as it moves through soil and rock. The minerals responsible for "hard" water tend to form insoluble salts, also known as scale. Formation of scale on heating elements reduces the efficiency of small machines. Aries Premium Drinking Water filters contain ResinTech MBD-80, a proprietary blend of a high capacity weak acid ion exchange resin and granular activated carbon. The ion exchange media prevents scale formation by reducing the calcium and magnesium associated with alkalinity. The granular activated carbon (GAC) reduces chlorine and enhances the quality and taste of the drinking water. The media is buffered to provide pH balance. Sized to fit standard Slim and BB housings.