Pro-Mix BX Biostimulant + Mycorrhizae - 3.8 Cu. Ft.PRO MIX BX is a solution for growers seeking to benefit from both the nutrient retention ability of vermiculite and a perlite content providing limited but proper drainage capacities. Combined with high quality fibrous peat moss, this formulation is ideal for growers looking for a general purpose medium which creates a well balanced growing environment.