Perlite is permanent, clean, odorless, non-toxic and sterile. Because it is sterile, "damping-off" is basically eliminated as well as disease, seeds, and insects. It does not deteriorate, rot, or turn moldy. Perlite is essentially PH neutral. It promotes faster root growth and quick anchorage for young roots. Soil mixes with perlite helps retain air, plant food, moisture, and releases them as needed by the plant. We offer the size commonly called "medium or horticultural grade" in the greenhouse trade. The granules of perlite that we sell are approximately the size of dried peas.