Diamond Crystal Red Out Pellets with Iron Fighter Formula is a typical 99.6% pure salt that is virtually 100% water soluble. This special formula is FDA approved to use when iron content in your water is high. Some of its benefits include: prevention of rust stains on household fixtures, decreases rust buildup, can be used in any water softening unit, minimizes mushing and bridging and keeps your water conditioning unit operating smoothly. Most importantly, the Diamond Crystal Iron Fighter Formula reduces softener maintenance costs.