Perlite is great for increasing the aeration and drainage of your houseplant's soil. When repotting your plants, add in a handful or two depending on how large the pot is, and mix it around to evenly distribute it. This 250g bag will be plenty for repotting a large plant (in a 35cm diameter pot) or 3-6 smaller plants depending on their size. 

Perlite is a naturally occurring volcanic rock, which is fired to produce little lightweight porous pebbles