Our 1/4" pumice is ideal those wanting a clean hand screened pumice for bonsai soil, soil mix's or to improve the drainage of water sensitive plants. Particle size is mostly 1/4 inch with some as small as 1/8 inch. Our pumice is a natural volcanic product mined in the Southern Cascades Mountains of Oregon. You get only clean pumice... no rocks, roots or other debris. Known as the "rock that floats", pumice has many tiny gaps or air pockets that allow roots access to oxygen, nutrients and water. Pumice improves both water retention and drainage of your soil mix. We ship our pumice by Priority Mail in boxes that are a little larger than the standard large flat rate square box. Our pumice is hand packed and bagged with a reusable tie for easy storage after you have used part of the bag. If your pumice dries before using, moisten it to keep dust from forming. Dust from any rock or potting soil product should not be inhaled and can be irritating for people with sensitive lungs. Our box contains 5 quarts dry measure. We are a commercial Wholesale / Retail Plant Nursery with over 15 years mixing specialty potting mixes. Check out our other listings of custom potting mixes to select the perfect mix for your plants. Pumice can not be combined with other items for combined shipping. Scenic Hill Farm is a licensed Oregon nursery -- license # L0170090NG.