I just recently received one of these ultrafire C8’s and on the one side it does say Cree xm-l2 u3 but I’m not sure I believe it, it is brighter than my XinTD C8 V4 with the xm-l2 t6 emitter by quit a bit. I liked it so much I went to order two more for friends and AliExpress is already outta stock, and I’m not sure when they’ll have more in stock. Its a real thrower and for $18.50 free shipping I couldn’t go wrong, but did take 3.5 weeks to show up.
The human eye really can't spot the difference in output between a XPG2 at 3 amps (about 750-800 lumens) and a XML2 T6 at 3 amps (about 1050-1100), so I find it hard to believe the difference between T6 and U3 would be noticeable to anything but a light meter. Remember what Feynman said, the easiest person in the world to fool is yourself.
Your probably much more knowledgeable than I am, and my test wasn’t very scientific, I just shined the two lights on a wall and both myself and 4 other people all agreed that the ultrafire was brighter than that V4 XinTD that I also own. So no meter was used just 5 people’s opinion. Either way for $18.50 this light is well worth the money and I’ll have no problem selling them here in Montana where the best light you can buy is a mag.