Plant!t, 10 liter, horticultural clay pebbles, 8 mm-16 mm pebble size, made from 100% natural clay, are clean, ph stable & offer great aeration & drainage, especially in flood & drain, deep water culture & drip feed systems, due to their unique structure & ability to cover a large surface area, offer the ideal environment to foster beneficial bacterial growth around the root zone, leading to naturally healthier plants.