Reptisun isnt enough uvb, neither is the 1 or 2 diodes included in narrow band chinese LEDs. You need to get an arcadia brand t-5 fixture, and be sure to use the 14% UVB bulbs. They have to be RIGHT over the plant you wanna boost thc & resin production in. Unfortunately, the uvb dissipates fast - the lower buds will show no apparent effect, but the tops are OBVIOUSLY blessed with increased resin & thc production. I prop mine at ~a 45degree angle, to avoid blocking light from above. Best use is with a light rail, imo. I have seen zero additional benefit using UVB during veg or even during the first half of flowering. Plants that received it for the duration of flowering, showed the same - but not more- resin & thc production as the girls who only received uvb during the last few weeks of flowering. To save $, I only use them for the last 3 weeks of flower myself. It IS real, though. I live in WA where weed is legal (I LOVE THE FUTURE!!! Lol) and am able to walk in and submit samples to 360-Analytics, for thca & thc, testing which happens to be down the road from me. Havent done a properly controlled uvb experiment in years, but when I had the $ for it (its $25+ to test each sample, depending whatvu want - terpine analysis, cbg, cbn, molds, fungi, etc), I was seeing 3-5% bump to thcs, & an obvious to the eyes, increase in resin production. No change in flowering times noticed. And when I say “3-5%”, I mean 21% thca, increasing to 24-26%... not just 3% of the total, if that makes sense. Generally, its about a 15-25% increase in potency, seen in the uvb treated tops. I also wanna mention- topping & ScrOGing short Indicas lends itself PERFECTLY to this method. When the plant is only 12”-18” tall, and is basically just a mass of 9” colas, every bud can be hit with uvb, and the entire yield is equally killer. With anything past 18” tall or so, the mid-bottom buds just arent getting enough uvb to matter as much. Best results with a light rail, using very short plants, topped and ScrOGed so that no one top is taller than another. I used to keep this shit secret at all costs, as it really does give you an edge over those who arent using it. But as Ive aged & matured, Ive evolved my thinking & believe that useful info should be shared freely. This is VERY useful info & I highly encourage those who havent tried it, to do a side by side & see for themselves. Its maybe $75-$85 for the T-5 fixture plus the 16%uvb bulb. Not sure of the current price, its been a while since I bought one. Bulbs are in the $30-$35 range.