Protected 14500 works fine.
=the=
You can use both without problems.
Thanks!
I own the SK58, and I like it a lot. I would go for it just for the handsome styling.
Doesn't it look exactly like the SK78?
I posted a comparison between the SK68 and a similar (zoomie), the Torch Light C78, plus the better-made but more of a unitasker Hugsby P31 here:
https://budgetlightforum.com/t/-/1654#comment-55667
I also owned an SK58. The thing I didn't like about that one was the LED which came with it, which from what I've read here, must've been an Osram Golden Dragon. Pretty lame and blue on 1.5v AA. Now, on 3 volts or more, it does quite well and does not seem as blue. I still prefer Cree any day. However the ones which are verified to have Cree's inside are all in the $10+ range from what I've seen, and at that point you can get an SK68. The SK58's with non-named (Osram) LED's can go down to an amazing $5 or $6 with free shipping, at which point (at least I) start to feel guilty wondering how they are making them so cheaply, because they are made out of metal (and beat the "feel" of any big-box store-bought plastic piece of junk any day). If you get an SK58, you should have 3 or 4 volt 14500 batteries to use with it IMO, just resist the temptation otherwise. It became my girlfriend's first single-LED flashlight, and, not knowing any better, she liked it on AA, but since I've had her using it with a LiFePO4 (3 volt) 14500 and it's twice as bright, and likes it more. She uses it quite often (short runs), and it's small enough for purse carry.
The size (and many would say the feel) of the SK58 is better (smoother, and narrower) albeit with a narrower lens, which is not going to help performance, but it still works fine. So, performance-wise, the SK68 is probably the best, plus it has a clip, but 1 of my 2 SK68 clips stripped off (see above post). If I were pocket-carrying only... and a lot, I'd go for the SK58 with a Cree. Otherwise, I'd recommend the SK68 with standard provisos and cautions.
I don't own a SK78 and am not interested; no particular reason, just my spidey sense. I guess it seems a little wide, 'all the way down'. No clip, roll-away... I'm not seeing the superiority to justify charging more money for it.
Are you sure that the Sipik SK58 can use 14500? Never seen that anywhere. Where did you buy it?
of 5 that I have all have a noticable cree ring , just screw off bezel for easy access an paint it made a great improvent , as for the tailcap being hard to remove "say wat " , prehaps if your disabled you may be challenged
of the sk68's I have the sipik and a couple of ultrafire branded models there a prettywell identical both use the better solid pill , I also have a mxdl branded sk68 that has a hollow pill , as for using 14500's no problems I have been heavily using them nightly for bout 2-3 weeks with out any probs , and light still fuctions perferctly wen returning to AA's
An update. Had the SK58 and SK68 dissembled at the same time.
The pills are different, and not interchangeable. They are of very similar width, so much that they look like they'd interchange (or at least thread in), but they do not not. The widths are slightly different and the threading seemed different, to my memory. The SK68 pill is longer/more mass, with longer threading of course. Seems higher quality. I don't know why they'd machine them so similarly and not make them with the same threading and widths, when the differences are so slight.
The tailcaps look different, but ARE interchangeable. They both actually look pretty good on each other. The internal switch seems identical.
The SK58 doesn't zoom as wide (the lens is narrower). They both zoom in similarly. That's hard to tell, because my SK58 doesn't have a Cree die, but the die sizes are at least similar (not sure if exactly the same). IIRC the SK58 is just a tad longer than the SK68, but it's narrower.
After doing A/B tests, the SK68 with the Cree LED pretty much embarrasses the SK58 with the Osram LED, no matter what battery I choose. I'd say the most noticeable difference is on 14500, where the SK68 with a Cree is quite nice, even if you're a little jaded with flashlights. I attribute this mostly to the LED; not sure how much the driver plays a role here (if there even is one). I'd like to have a Cree-equipped SK58, if for nothing else than to satisfy my curiosity as to how it'd compare. Ergonomically and cosmetically, it is superior. In every other way though, it seems inferior.
Question: isn't the SK68 is a costmetic copy of a high-end flashlight? If so, which one?
The SK78 cost more than the rest but looks like the SK58. I wonder if the SK78 has a Cree or an Osram emitter?
Nitecore Extreme, IIRC, even though the NE is not a zoomie.
EDIT - Yep. Pretty identical cosmetically.
DOUBLE EDIT - When will some manufacturers realise that raised clickie boots ruin tailstanding. At least Sipik didn't copy Nitecore's error there.
I don't consider it an error. I have very little need to "tailstand" but like the button to stick out so it's easy to get to especially if it has a momentary feature which I like.
The Sipik SK68 tailstands but the clickie it very accessible and easy to use no matter whether you use thumb, index finger or little finger. There's no reason that Nitecore could have done the same proving for everybody's preferences.
Is at Manafont....Q5.
Not at all (rude bugger
).....But a bit of knurling on the tailcap would make it much easier to remove with oily/greasy/wet fingers.
that gave me a laugh Tas 
I dont have any troubles with it but agreed some knurling wouldnt go astray
checkout 365digital
he sells the ultrafire branded sk68's $7.49AU delivery included , I puchased from him and both lights I recieved had the solid pill , I found the link to him from an old post here at BLF
A couple of notes for someone searching in the future. Apparently there are different versions of these lights. I put a 14500 in mine (SK68) and it quit working instantly.
The SK78 looks similar to the SK58 (I have the SK78). The SK78 is slightly more expensive and doesn't have all the sharp edges/angles of the SK68 but the SK68 still seems better made. The pills are interchangeable however with a bit of a "push" :) I took the pill out of the SK78 and put it in the SK68. The lenses are the same size as well.
I haven't tried a 14500 with the new pills (for obvious reasons).
I'm curious if anyone with the SK68 has managed to clean up the beam of the rings. I've done something similar with an aspheric before but haven't done anything to this yet other than remove the metal disc. I'm planning to paint the Cree ring and retaining ring at some point.