I’m pretty sure this U2 4C is just T6 4C. U2 4C doesn’t exist even in Cree’s datasheets. Probably one of FT’s suppliers lied to them. There’s no U3 in Tangsfire either - it’s just heavily driven T6.
Curious to see your comparison pics on these.
-Garry
I had actually fried the led’s on both the s3 and m2. I had dedomed the led’s and they worked for a while. I think what finally killed them was using them on my bike during the day in flash mode. The led just fell off the star most likely from overheating. I’m pretty new to this modding stuff but I was able to copper braid the springs in all my lights and this is only the second time I have swapped an led from one of my lights. I did this using a $7 harbor freight soldering iron. I also changed the exposed wires from the driver on my s3 with some 22awg silicone wire I ordered from fasttech.
+1 - no such thing as a U2 4C most likely. 22 gauge from FT - not too good, I'd stay away. Your really should use the better 200C rated silicone wire - that's what we all typically use. For LED's to fall off the star takes a lot of amps or force - really should use copper stars. Your really need to hit Richard at mtnelectronics.com for high qual parts at competitive prices.
Already ahead of you… see post #14 
I am not ordering from fasttech unless I am in no hurry to receive my order. I have placed 2 orders from RMM and plan to keep spending my money domestically. I have my eyes on a couple of items sold through illumination supply.
Cool! RMM is wayyy too accomodating. Since he is a crazy hobbyist like the rest of us, he seems to only carry stuff we are looking for... 
Convoy M2 Noctigon xml2 t6-4c
Convoy M2 Noctigon xml2 t6-4c
The picture of the M2 close up to the wall came out yellow no matter which setting I changed on my galaxy s3 phone.
I did an interesting comparison today:
Test Setup:
- SolarForce L2 host (little customized) used for both P60 pills for comparison
- two P60 pills - flattened pill top, both with a FT 6x7135 2.1A Nanjg, 22 AWG silicone, little dab of AS5
- identical parts for each P60 drop-in (SMO reflector, etc.)
- Samsung 25R cell (overkill, but should get max amps)
Test Comparison:
Results:
- XM-L2 U2 4C/aluminum: 2.12A tail, lumens: 578 @start, 547 @15 secs
- XM-L2 T6 4C/Noctigon: 2.13A tail, lumens: 626 @start, 605 @15 secs
Conclusion:
Well, two variables: the LED and the MCPCB, but the IOS T6 is ~10% brighter than the U2. Both beam tints looked about the same, but I did not compare side by side yet.
So, is the FT U2 4C really that worse than a T6 4C? Hhmm, you'd have to look at other test data comparing copper (direct thermal path) to crappy aluminum. According to Match's tests (https://budgetlightforum.com/t/-/16621), it should account for ~6% difference I'm guessing at this amperage of 2.1A. Possibly in my simple test, maybe as high as 10% with variations, then you could only conclude the listed U2 4C is in fact a T6 4C, or maybe worse, a T5 4C? Match did use a 20mm SinkPAD, so could be characteristic differences in performance in this range of amps.
Thanks Tom.
Basically same conclusion as I did some some months ago here. (Just did a minor edit where I wrote 3C one place)
Certainly not U2, probably T6, if not worse.
Nice to see very similar conclusion based on different tests. :)
I can't get to that post - do you have a post #?
I was thinking this might have been done before... I had one of the FT ones in a bin, and was planning on using it in a zoomie upgrade (previous mod) and wanted to get an idea if any good. I like the neutrals soo much more in zoomies.
Post 305
I have ordered some of those U2-4C, they are XM-L2 T6-4C, the T6 is the bin, the 4C is the tint…very neutral and the colors from the emitters are very vibrant and more “true” than with 1A…I have one in my Ultrafire SH98 on a 20mm sinkpad, and one in my Ultrafire F13 on copper sinkpad (both are epoxied to the pill) I just upgraded…at 3A~ they are INCREDIBLY bright and don’t have too much yellow in them or too much white…my favorite tint 
How do you know they are T6, and not T5 for example?
i unno
If i’m not mistaken, 4C tint (warm white) is not available in U2 ? (I see xlamp specification only mention about T6/T4 highest on those tint)
You are right about that. The highest bin for NW/WW is T6 according to the datasheet.
My test results above in post #22 put it in the T6 or T5 range, just not sure. Didn't have time to move it to a Noctigon and re-test -- should have though... It's not a bad deal if it's a T6 at that price.
I think maybe they(cree) have some special U2/3 NW/WW (also very rare), but I don’t think it is commonly available. (needs alot of odd to get high bin in these warmy colour)
Oh by chance I put one of these in a crappy glove-box light with a 1.4a Nanjg 101 with a PMMA lens.
The tint is a very clean white overall with a very minute pinkness, almost can’t see it.
I’m not really experienced enough to comment on any other aspects of it though! I’m impressed at the brightness for 1.4a. Almost as bright as my H600FW being driven (factory) at 3.8a which kind of puzzles me.
I bought those XM-L2 “U2 4C” LEDs too, I don’t care much for the loss in brightness (since they are not real U2s) but FastTech (or any other seller) selling them as such is unacceptable.