The RAW Hydrostone is made from uncoated natural terracotta 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 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. B00HFZE6G2