Leca Clay Orchid/Hydroponic Grow Media - 4 lbs. Made of 100% natural clay. Pebbles are of uniform, round shape. Inert, pH-neutral, clean and decorative. Comes in a 2 lbs. package. For Orchids - porous structure provides excellent aeration and acts as a water reservoir. The size of the pebbles is perfect for medium to large Cattleyas and Laelias. For Hydroponics - Ensures good root aeration and prevents rotting, excess acidity and soil pests.