All Natural. Made from the bark of fir trees. Hygroscopic. This means it absorbs moisture and then releases it, creating humidity. The perfect substrate for humidity loving reptiles. Conducts and evenly distributes heat. Adds environmental stimulus. Allows natural digging and burrowing activity. Absorbent. Pulls icky waste away from your animal. Decorative. Provides your terrarium with that natural tropical rainforest look. Re-usable and super easy to maintain. All you have to do is soak in hot water every 2 to 3 months for fresh, clean bark. (ReptiBark should be replaced at least once a year). Smaller chips provide better moisture retention (increased surface area). Prevents live food from hanging out in your substrate (small pieces interlock).