I have known of these bags for awhile. I have not added to my setup yet,but has to be better then a yeast/sugar mix.For a small set up they are perfect and not at a bad price.My shop sells them for 34.99.According to my hydro guy,1 will put 4x4 grow area at around 1100 and 2 bags well above 1500.Just thought I would see what the good people at had to say.