1/4 - 1/2" Natural Cascade Mountain Volcanic Lava rock for use in soil mixes for Bonsai, Succulents, Cactus & soil mixes for specialty nursery plants. Also for top dressing bonsai and terrariums. Pleasing mix or red, grey, black and white. Approx. 5 dry quarts volume. Neutral PH, doesn't rot, all natural, relatively light weight and porous.