Roots Organics HPK Bat Guano and K-Mag is extracted from our unique natural sources of phosphorous and potassium. Bat guano, renowned as an organic source of phosphorous, is combined with Langbeinite, a natural source of potassium mined from ancient sea beds in the American southwest. It is then minimally processed and immediately available to you, the consumer. Your flowering plants will thrive because this Roots Organics process preserves all of the benefits and synergistic qualities found in our ingredients. Size: 2.5 Gallon. Additional Sizes Available.