These special Eurorocks are the BEST! Light weight, very clean & much easier to reuse, they are the perfect choice for soilless growing. This media is round with no sharp edges and a high air-holding capacity. May be mixed into other mediums. Used for orchids, veggies & many other plants. They offer better growth & higher yields than any other grow rock available. Hydroton comes in two sizes; a small 4-8mm & the standard 8-16 mm. The smaller size is the most preferred for blending with other mediums such as Rockwool & Procoir. Suggested Mixes; 40% Procoir & 60% 4-8mm Hydroton.