This is Professional grade Perlite. The size of the pieces ranges from 1mm to 6mm and is classed as Super course. Each bag contains approximately 4Lt of substrate. This can be used neat to root cuttings in or use it mixed into a compost of your choice at the rate you want to use it. On the nursery we tend to use it at between 10 and 20% mixed into a professional grade compost along with a slow release fertilizer and vine weevil control. It is supplied in a grip seal bag so you can use as much as you need and then reseal the bag for future use.