Yeh. It’s good for The Muggle who wants that convenience, but the kind of people who’d choose a hi-performance light likely wouldn’t want that at all.
Well, I bought six (!) M21Bs from Simon so far! Two for myself (XHP 50.2 3000K/4000K) and four to make a nice gift to friends (GT-FC40, XHP 50.2s). These folks don’t know anything about batteries, just like me. These folks don’t own battery chargers, just like me. If there was no Keeppower USB battery, I would not have bought a single M21B as a gift, because it doesn’t feature an option to charge via USB. One person liked the M21B so very much that he chose to buy one as a Christmas present for his nephew. Ka-Ching!, sound of a cash register.
I’m not talking about some fancy nerd stuff here but about promoting business. And making the M21B able to support the proper use of 21700 USB batteries (more space needed!) would at least just be another plus factor to promote this very flashlight, while the pack of comparable flashlights features USB ports (Wurkkos TS21, Sofirn SP35 —> tried both of them, didn’t like either of them compared to a beloved M21B).
I want to underscore what I wrote before:
I’m not trying to tell Simon how to run his business, I’m just a customer who’s making a proposal 
What are the Convoy lights which come with hard anodising (Type III)?
I just think the word is relatively short, and its meaning is also very suitable for flashlights.
Could you upload a photo of your battery.
How about M21F ,the size is similar to M21B,
XHP70.2 ,SFT40,KW CULPM1.TG can be installed in M21F, it has Type-c charging port
mostly Type III,
M21F WOW what a nice looking light! Thanks Simon
You didn’t really respond to my two proposals/questions, but the M21F looks really interesting
He did answer your questions in a very diplomatic way 
Looks great. Difference between this and M21E?
Haha, was going to be my question. Looks brilliant! I just had a look but it’s not showing in his store yet.
I’m wondering this as well. I’d be very interested in M21F with either a GT-FC40 or a B35AM.
Does it use the same reflector as M21B and M1? Will there be an orange peel option?
Seems like the head is smaller. M21E uses same size reflector as C8+.
Hmmm. M21F looks great… b35a in this would probably be most attractive.
Simon, what is the bezel OD and reflector ID + height?
Looks to me the bezel is roughly 38mm?
New M21F looks great. I think it is use same driver of M21E. Also hope Simon to release in some point GT-FC40 driver for it as many of us wait that from long time. OP reflector I think it will be added to XHP70.2 version anyway.
When will this be available?
M21F SFT40 / KW CULPM1.TG 8A or 6A ?
How does the beam profile of the M21F compare to the other M21 series? I hope it is floodier!
Interesting, thank you for the explanation! Short is good…it would be difficult to engrave something like “Destroyer Of Darkness” on a host, wouldn’t it.
Now I desire a M21F with a B35AM, but if not I can settle for the SFT40 or XHP70.2 (or just buy one of each 
).