The RAW Hydrostone is made from uncoated natural terra cotta clay, kiln-baked. It was originally developed to keep tobacco fresh on ships during the early days of modern trade. Allow the stone to soak in water for 5 minutes. Then place it with your tobacco or other legal herbs. It will keep your material fresh for a very long time. It can even bring old dried material back to life and is 100% reusable. Serious game changer brought back from the past!!