PRO CAL 20 PLUS is derived from Calcium Carbonate that has gone through a proprietary process to render its particle size to less than one micron and completely water-soluble. This high level of solubility elevates Pro Cal 20+ above all other Calcium sources currently on the market as a source for a nutritional Calcium. Pro Cal 20+ also contains a plant-derived protein Nitrogen that has been proven to facilitate uptake, use and transportation of Calcium within the plant. PRO CAL 20 PLUS also contains our proprietary Freshwater Algae Extract (UNI-MAX) which elicits even greater plant response.