Pro-Mix 2 cu. ft. Ultimate All-Purpose Plant Mix Compressed Bale. It expands to 4 cubic feet of growing media, making it suitable for all indoor and outdoor planting applications. This 95 percent peat-based formula contains 5 percent perlite, limestone, a starter fertilizer, and Mycorrhizae, a natural plant stimulant that assists plants with nutrient and water uptake for improved plant growth and resistance to stresses.