ppfd is an important factor to look at when researching for your light purchase. but there's others as well , spectrum , reliability [many reviews to read] , quality of drivers , diodes etc....... Spiderdog , i believe has pointed you in the right direction with HLG. don't do what i and many others have done and that is cheap out with an Amazon led. i bought some hollandstar leds and they vegged well enough but i didn't get the size and trics with the buds i wanted. take my advice if you'd like but from my experience and others too is don't cheap out ! you'll end up like myself and others of having to buy again. remember that for the most part you get what you pay for and research ur azz off too , it pays off ! Black Friday deals are coming too , best way to buy after a shiite ton of research , good luck and happy hunting !