It is Magnesium Sulfate heptahydrate and more specifically 16% MgO magnesium oxide soluble in water
32.5% SO3 water-soluble sulfur trioxide comes from natural Kizerite. The only difference from Kizeritis is the higher water content. It is completely soluble in water and is therefore suitable for hydro-lubrication and foliar fertilization. Ideal for immediate corrections in acute magnesium malnutrition.

It is approved by the European Union for use in Organic Agriculture.