Terry Naturally® Silica-20™ - Plant Sourced is an aerial extract of the herb horsetail that features silica through a patented extraction method. This method involves filtering out the insoluble parts that are abrasive and harmful. It is entirely soluble and virtually 100% absorbable. Silica-20 enhances the adherence and absorption of calcium into bone tissue and has a positive effect on collagen metabolism, and supports healthy hair, skin and nails.