The mix is composed of 3 parts: Lava rock, Japanese Pumice, and Hard Akadama. Akadama works wonder for bonsai due to its ability to retain water and drain well. To add onto these benefits, Akadama breaks down well over time. We wash and screen the lava rock along with the clay removing larger pieces, making this premium soil ideal for smaller trees. It allows for better drainage, and better ramification of the roots system. The mix looks great in pots, the lava rock adds a nice red color to the mix.