S.I. (Structural Integrity) is the newest addition to the Humboldt Nutrients family of products. This silicate additive is formulated to supply your root zone with the silicates your plants need to build strong, thick cell walls and cellular membranes. When your stalks are stronger your plant has the ability to hold heavier fruits and flowers, which means less time staking your plants for support and more overall production. Note: not for sale to Canada or Oregon.