Orchid Supply Store uses Rexius Western Fir Bark which is heat treated and sterilized. This is one of the most important ingredient used in orchid potting media. It has a rough surface for roots to cling to and does not compact allowing air and water to pass through the root system of the plant. It is also high graded and sized to meet the highest standards of orchid growers today. Not only for growing orchids it is a decorative cover for indoor and outdoor pots or planter boxes, or a lightweight drainage material in the bottom of all your potting containers.