Hmmmm, now I’ll be researching whether my k18 has a protected circuit. As far as Li-Ion, the IMR’s are fairly safe - and you can always use a protected battery (if it fits). I use 18650’s, don’t so much see the appeal of the 10440’s over the longer running lithium primaries, except for the pocket rocket WOW factor. I prefer the CR123 size for more power in a small package. Years ago I used a mechanical ecig that took 10440’s, lasted about 3 hours between charges!
In case anyone cares, and since this thread is all over the place anyway 
the 2017 version of the k18 does have OD protection:
http://www.ultratac.com/faq-items/does-the-k18-have-over-discharge-protection-for-10440-batteries/
so this is the rev. 4 model?
I do not know the Rev Number, there are no markings on the packaging to indicate Rev Number. But if I had to guess, I would say yes.
What makes you ask?
Maybe contact Countycomm to ask what Rev they were selling in December 2017, and share what you learn.
sorry to tell you, but i can’t remember why i asked, now. i also don’t remember what i had for breakfast, and it’s currently lunchtime
lol
I think you wanted to figure out if it is Rev4 (it probably IS), because you assume, as I do, that they started using N219c in Rev5, and like me, you know the N219b is better, less green.
and, Yes,
I remember you want to buy my Maratac 
dont forget to send the money
…it’s starting to come back to me
i’ve got about 10 of them now, and i think that’s being conservative. 4 copper, 4 titanium, 4 black aluminum, and that doesn’t include the worms
sooooo are those Rev 4?
and Got Nichia?
i know 2 have nichia and…ooohhh, pretty butterfly…
where was i?
better yet, who am i?
Now I do not know whether I was then a man dreaming I was a butterfly, or whether I am now a butterfly, dreaming I am a man
∆ and/or:
Which side of the aquarium glass am I on ?
How many sides are there…
A man went to sleep and had a dream he was a Copper Maratac, when he woke up he did not know if he was a Copper Maratac dreaming he was a man, or a man selling a Copper Maratac.
A man named jon went to sleep and had a dream and was blinking his eyes real fast and didn’t know if he had PWM or not
Then PWMWarrior awoke with a start and Shouted out in High CRI
NO! None of my Maratacs have PWM!
and a great battle ensued, in which the maiden was saved, and PWMWarrior lived happily ever after.
bump before withdrawing this sale
ok, withdrawn