Perlite and Vermiculite have many uses in the hydroponics and horticultural industries as a growing media.
While they can be used 'as is' directly from the bag, many growers mix different ratios of the two together to make a blend that best suits their requirements. This way they get the best of both worlds - good drainage and good water holding capacity.
Mixing them into cocopeat (or soil) will aid in the amount of air trapped within - improving drainage and root development.
Grade 3 - Coarse
retains approximately 50% of it's weight in water