What tactical_grizzly has suggested makes a lot of sense, however I personally am more of a fan of the lower CCT ranges and would love to have all the options there, i.e. 4500K, 4000K, 3500K, 3000K & 2700K.
Nice those M21x releases. And more 519A CCTs coming. Wonderful news.
Does anyone have a photo of a M21C and M21D side by side? Interested in seeing the difference in the middle (button section), e.g. where will my fingers on the underside end up. The tube looks shorter on the M21D.
Here’s a size comparison from my Convoy Guide. It’s the product photos scaled based on the lights’ listed dimensions.
^ thank you for this! Much needed for this thread
Would be nice to also include S and L series for size comparison
Hmmm, I notice that there doesn’t seem to be much interest in 5000K 519A. I am looking forward to 5000K because of the tendency for neutral CCT 519A’s to be overrated in CCT, plus the tendency for reflectors and TIRs to warm up the beam.
I’ve seen a review that measured S21D with 4500K 519A’s to be below 4100K. So if this trend continues, one would need to start with a 5000K rated emitter to get a beam around 4500K.
I’m interested in 5000K. In poll there was only one option and for me 5700K is better, if I’m dedoming or mixing tints for lower duv.
Thank you, that’s perfect!
Awesome! Cant wait to grab a M21f and M3-c GT-FC40!
I would also be very interested in a 519A in 5000K.
The TIR certainly warms the CCT in the S21D.
I had noticed just through simple observation that my 519a 4500k was warmer than my other 4500k LEDs. So that makes sense. And I'm personally interested in 5000k 519a bc my hope is that when dedomed it will warm up around -1000k just like the (4500k) has been doing, and that would land me at my optimal 4000k cct. So I'm excited for 5000k personally
The following is a curious question: What is the size (diameter) and emitter spacing of the Convoy S12 MCPCB host?
It looks like it is slightly bigger than ∅20mm. ∅25mm maybe?
I am wondering if it could be possible to fit this “3TI” MCPCB from Kaidomain. With it, all led emitters could be arranged in series and driven with a boost driver, for a fully regulated, full power blast no matter battery SoC flashlight.
Knowing the distance between led pad centers is the key parameter here, I guess. But at first sight, I'd say it looks like it would fit fine. 
I can’t quite fit my calipers all the way in to measure on my S12 but it appears to be 25mm, give or take 0.5mm. The emitters look to be about 6mm from the center of the board to the center of the emitter.
I didn’t have time to label them all or add more, but here’s the rest of the Convoys I had in my flashlight size comparison file.
I’m adding in this line of text to make it clear these are two separate images at different scales.
Actually, maybe Simon can order an S12 MCPCB that has the LED in series 
Imagine efficient triple boost driver Nichia 519A S12s 
Wow that is exactly what I am looking for! I will definitely buy this if it comes with a buck or boost driver.
This may interest you. Not exactly a floody L7, but it’s a floody two cell light that’s very bright.
Thanks very helpful. Will help me decide which GTFC 1800k host to get!
I saw that one but Nightwatch drivers are the typical direct drive with no regulation and very inefficient. I want a buck or boost driver with good regulation and high efficiency. I’m spoiled by Olights and Fireflies with the LUME driver. They can sustain a very high output for a very long time unlike the toy lights. Convoy has some lights with good boost drivers too so I’m interested if Convoy makes a similar light.