I have a newtek 4ft 8 bulb t5, my brother used it through his last grow and just switched out the bulbs to flowering ones and he yielded pretty good. my t5 puts out 40k lumens....just keep it close to the tops. nothing will compare to a hps for flowering but they come with a lot of headaches too. fuckers run so hot my 400 was air cooled still hit 83-87 degrees. my t5 running over my babys its a steddy 77 degrees