Sul-Po-Mag 0-0-21.5 Sulfate of Potash Magnesia (K-Mag)"Greenway Biotech Brand" 5 Pounds 5 Pounds of Greenway Biotech Brand Sulfate of Potash Magnesia Contains 21.5% Soluble Potash, 10.5% Magnesium, and 21% Sulfur It is Derived from Sulfate of Potash-Magnesia Great Source of Potassium, Magnesium, and Sulfur for Your Soil