Custom Blended Mix by Orchid Supply Store is hand made when your order is placed. Made from the finest ingredients available & are perfect for the plants in your collection. 100% Medium Grade Rexius Western Fir Bark. Orchid Supply Store uses Rexius Western Fir Bark which is heat treated & sterilized. This is one of the most important ingredient used in orchid potting media. It has a rough surface for roots to cling to & does not compact allowing air & water to pass through the root system of the plant. It is also high graded & sized to meet the highest standards of orchid growers today. Not only for growing orchids it is a decorative cover for indoor & outdoor pots or planter boxes, or a lightweight drainage material in the bottom of all your potting containers. Orchid Supply Store Custom Blend Rexius Fir Bark Medium