My UniqueFire UF-T09 9X CREE XM-L is a 3x 26650 only light. But I can tell you once you use one of these longer lights with a side switch, as the UniqueFire has, you’ll never want to use one without it. It’s the reason I actually considered one of the variant 18x cree lights due to one version actually having a side switch. But I knew if would be very underpowered, and I didn’t feel the need to carry a 4x 26650 light.
One reason I bought the TrustFire TR-S700 which is a lot heavier than this is the format which is soupcan style but HUGE and with a handle that contains the switch and integral output adjustment which makes for easy one hand operation, so it can be done with thoughtful design. Expensive but actually a practical light.
Why? I use my 15x (4x26650) light one handed all the time, last night on a 1hr walk, I’d love to have a forward switch instead so I don’t need to use my other hand. I’ve always wanted one on my J18 too, and thats a much lighter light.
If it does have 21 led’s wired manually, it must have been a heck of a pain doing so, not to mention getting them all aligned correctly to the reflector. But it’s possible they created a pcb as was done with the Lightscastle 12x Ultrafire (SuperNight) flashlight.
Still, even if this 21x light was upgraded with a more powerful driver, no way do these types of lights have proper heat sinking to handle it. So far, the only couple of multi-LED lights that can handle much higher power than stock are the Trustfire S700 and the Trustfire TR-J20, just to name a couple of them.