[CCed from my Amazon review]
Really nice warm-white diving light!
Admittedly, I don’t dive, and am not likely to do so, but I do like the “waterproofness” of diving lights (like my Ultrafire DV-S9s) to be able to use them in any kind of weather without concern. So when I saw the WK20 listed, and in warm white yet, I had to try one. And then another. 
When I got it, I was pleasantly surprised. Even the box it came in was quite nice. Inside, the light was packed along with the manual, lanyard, charger, cable, and the included 18650 cell inside the light itself.
First impression was that this was a solid light, built like a tank! Nice heft, perfect semi-gloss black ano, a wonderfully springy magnetic side-switch… it just felt good to hold.
Didn’t even wait to charge the cell, just removed the insulating disc and fired it up. Nice incandescent-like warm-white light! It’s been ages since I’ve seen a light offered with a WW emitter, my last being a Sofirn SP36WW. And speaking of Sofirn, this light could be a clone of the Sofirn SD02 diving light (which I believe is neutral-white and not warm-white). So right there is a great sign that this’ll be a great light.
Externally, again, flawless semi-gloss ano, no chips or dings anywhere. Aside from the tailcap, I couldn’t disassemble the light further, so it might be glued shut to also help keep out water. A bit disappointing, as I like looking at the innards.
The UI is simplicity itself. Click on, click to advance modes, click’n’hold to turn off. Low-to-high, with memory. 5 modes, very nicely spaced. I thought I was at the brightest at #4 and gave one more click to go back down to low, but it got even brighter! :laughing: Nice!
The lanyard is a nice thick “rope” type with the little slider thingy attached.
The beam is pretty clean, nice round central hotspot, faint corona, slightly less-warm spill, but not fried-eggy in any way.
I did a quick dunk test for a while in a utility sink, and there was no indication of any water ingress, no condensation afterward, nothing. True, it’s not diving 100’ underwater or anything, but it’s something.
And the warm-white light itself is quite nice. Longer wavelengths (reds, yellows) tend to penetrate fog, mist, haze, etc., much better than shorter wavelengths (blue, violet), so I wondered why diving lights were almost always cool-white, which would just reflect right back in your face unless the water would be crystal clear. At least warm-white would penetrate farther in murky water. So even if I don’t dive, the WK20 would be the perfect light to use in fog, mist, haze, rain, etc., not just because it’s waterproof, but for better “reach” than a cool-white light.
And outside, especially with greenery around, reds and browns just pop under warm-white light, whereas they’d be washed out to faded dark-pink and gray-brown under cool-white light. Quite nice!
Basically, I can’t find anything about the light to even nitpick about. (Okay, maybe the glue, as I want to see the insides, but… 
)
Definitely recommended, even if you have no intention to go diving.
Addendum for the WK20S I tried adding but was rejected as “you already reviewed this product”. :confounded:
Great successor to the WK20
I got the original warm-white WK20, and it’s an incredible light. When I saw the WK20S version came out, I wanted to give that a try as well. Twice the output in the same package as the ’20 seemed incredible as well, but it’s true. :laughing:
Most of what I said about the ’20 applies to the ’20S as well. Awesome fit and finish, great switch-feel, nice clean beam, there’s nothing not to like, and I tried to nitpick on at least something.
So I’ll concentrate on the differences instead. Yep, it’s twice the output, 2000lm vs 1000lm. And it’s neutral-white vs warm-white. Lots of people have a hard time adjusting to WW, so NW might be a better choice for them, although I love the look of WW light when outdoors. Natural colors just pop under WW light.
Also, the ’20S loses moonlight mode, so if the ’20 had levels 1-2-3-4-5, the ’20S only has 2-3-4-5, if that makes any sense. I like the utility of having moonlight mode, but maybe people who prefer to not have to cycle through 5 levels would prefer 4 instead.
That’s really it as far as differences: 2000lm vs 1000lm, neutral-white vs warm-white, and no moonlight mode. Everything else is the same between the ’20 and ’20S.
If you like the WK20, you’ll like the WK20S as well. Definitely recommended.
