The gray lava rock from Japan is especially suitable for bonsai designs. The rocks are very interestingly shaped and their hollows and protrusions provide ample space for substrate and roots. In addition, wires can also be attached to the rock with adhesives. Thus, you have almost unlimited possibilities to plant the stone. In addition, you can also use tile adhesive, for example, to join individual stones together to form a larger, very individual and expressive stone.