PRO-MIX® HP (high porosity) provides a superior growing environment for plants that require increased drainage and oxygen. In addition to Canadian sphagnum peat moss, perlite, major- and micronutrients, and dolomite and calcitic limestone, it's fortified with beneficial endomycorrhizal fungus to strengthen roots and increase plants' ability to fully utilize available nutrients. 3.8 cu ft of compressed PRO-MIX equals about 7 cu ft in use.