For maximum lumens, I would go with XHP50.2, but it looks like it is no longer available.
https://www.aliexpress.com/item/4000333646371.html
Since that seems to be gone, I'd go with the SST40 version.
50.2 isn’t a thrower. With the thermal limitations of a host this size sustained lux will be worse than a s21b+pm1
You just said above that you might get something less pocketable
@PiercingTheDarkness
Yes but I mean something ~M21A sizes 
Anyway, thanks for suggestion. Maybe on photos it’s bigger than I think.
Oops.
I changed my mind about the BLF-D80v2.
At $27.70, it's a good deal, but right now it's at $37.70, which I think is too much.
Sorry about that.
I read a topic about this flashlight and for BLF member it should be 27.70$ (or it was months ago). I will try to buy it with discount maybe, which one will give me better throw?
Spend a few $ more and get a noctigon KR1
Actually $28 ($33-15%)
[quote=zamachowiec]
I like this idea I am going to do it to my M21B where do you get your dual springs from?
Zam get the M21b great size that’s if you have 21700 already.
I just use a single one of these over the top 
just don’t do this on the head in case it delivers too much current. Using the 30Q I measured 8.4A at turn on, the LED peaks at around 9.4 ish so 8.5A is fine. I’ve sold plenty and haven’t had a single issue. Not sure what you’d use for the 21700 though
Thanks for that just went to order the parts but cannot find the ramping driver?
I will add that the only reason I have dual springs is because it’s a gun light, stops the battery disconnecting with the recoil. A single one of those springs would be enough.
Installed a BeCu spring I got from BlueSwordM in the Sofirn C8F and that Convoy spring performed the same in it, so you should only need the single spring
Sweet never looked at that one because it had SST40 on it.
Now just need to go order all the parts thanks for all your help. Nothing better than a light that can work so hard you can blow the LED up in it love it.
thx
I already have it in KP CSLPM1.F1 green but don’t really like the green. I will be swapping the driver & LED out with Funtastic suggestion. It’s very easy to do if you have a solder iron. I just built a S11 XHP70.2 did not relies it was so easy.
I also have the 8A C8+ Osram CULPM1 great light. The M21B is a perfect size and I prefer the 21700 cells.
later
Careful soldering a spring as you can quickly melt the switch, I’ve done it a few times.
Anybody with the M21A and M21B and C8+ to check for lego-ability of the battery tubes?