This coarser mix, allows for better drainage, and better ramification of the roots system. The mix is composed of 3 parts: Lava rock, Expanded Clay, and Pine Bark. We wash the lava rock, and screen the pine bark prior to blending. This removes any fines that may cause excess water retention. The mix has equal parts of the lava rock, and expanded clay and has 1/2 a part of the pine bark. The mix looks great in pots, the lava rock adds a nice red color to the mix.