Hydrofarm (2) Super Coarse Perlite Soil Aeration Volcanic Rock Bags - 100L Each Unique volcanic mineral which expands from four to twenty times its original volume when it is heated Each particle is covered with tiny cavities that hold moisture and nutrients that are essential to plant roots The physical shape of each particle allows for optimum aeration and drainage Perlite is sterile, meaning it's is free of disease, seeds, and insects Weight: 22.4 lbs.