There are two product families, the S grades and R grades. The S grades are standard iron grades with a purity level of approximately 97.5 percent. The impurity is comprised of carbon, oxygen and nitrogen and is the cause of the iron particle’s unique onionskin structure. R grades are high-purity iron grades with an average purity of 99.5 percent. Through a hydrogen reduction process most of the residual carbon and nitrogen have been removed from the iron particle producing a higher purity iron grade which is lower in durometer hardness and lacking the unique onionskin structure.