N-P-K, nitrogen-phosphate-potash or the amount of each desovable within the mix itself for vegging you want something high in nitrogen low in p-k for flowering you want something higher in p lower in N-K last 2 weeks of flowering no nutz at all to deminish harshness of smoke also aggre harmoni about the foxfarm grow big an tigerbloom great for beginers easy to use pick up a bottle of superthrive while you at it as well