Adds environmental stimulus. Allows natural digging and burrowing activity. Provides your terrarium with that natural tropical rainforest look. Re-usable and super easy to maintain. Reptibark should be replaced at least once a year. All Natural! Made From The Bark Of Fir Trees Hygroscopic. This Means It Absorbs Moisture And Then Releases It, Creating Humidity. 4 QUARTS/FOR 5-