PRO-MIX HP with MYCORRHIZAEProduct Description With its high perlite content, PRO MIX HP provides a great growing environment to growers looking for significant drainage capacity, increased air porosity and lower water retention. The added benefit of fibrous peat moss and coarse perlite makes this formulation ideal for growers who require a superior quality product adapted to their needs for watering flexibility and crop seasonality. Product Details HP High Porosity Size: 3. 8