Back when I started with orchids we used a tradition old English method time consuming and difficult and you really had to know what you were doing precisely to do it. The best thing that happened is that back in 1950 they manu transitions from the old traditional methods of the 1800s into growing orchids into bark and bark mixtures and the barks that we use are typically fir barks. They come in a variety of sizes this happened to be a medium sized bark. When people tend to find out what prices they tend to go and find mulching bark from a local nursery - not a good idea. That local bark is for rocks, dust and other debris so stick to the fur barks from a reliable provider.