It comes with instructions for how much you should use in the boil. You can also use it for "dry hopping". It's very convenient and stores in the refrigerator for a very long time without losing potency. The only real drawback to the HopShot is that it can form a very sticky oil slick on your kettle and fermenter. A friend of mine said that if you only add small doses like 1/8 at a time, waiting 20 seconds in between doses (or something like that), then the sticky oil slick might be minimized.