Bamboo has been used as a substitute for parts of this product which would usually be made from plastic or other synthetic materials. While it looks and feels like wood, the Okiyo Sora Ball Pen is made from bamboo, which is a type of grass. It grows incredibly fast and can reach full size in a fraction of the time it takes for a tree to grow. This makes it a highly sustainable material, which can be harder than oak, depending on the type and species.material: bamboo & ABSwith black German inkproduct has been pre-branded with the official Okiyo icon to authenticate that it is part of our eco-conscious collection.