The original 18350 batteries I bought are the color in the picture on the EBay site and were NOT protected. I bought mine from Batteryjunction.com, and they note "This cell does NOT have an integrated PCB. Please be sure you fully understand how this product functions, how it should be charged and discharged and the proper handling of this battery type before attempting to use this battery."
I have since bought other ones from
MadVapes LLC and they ARE protected, and the color was royal blue. But the madvapes.com site also mentions "Pictures are approximate. Battery labels and colors may vary slightly at times depending on the manufacturer but always high quality, protected and the rated mAH."
The one that came with my Indulgence extended cup was that royal blue color but the size of the 'button' on the positive end is larger than the the button on the one I got from Madvapes.
I gather there is a difference between 'overcharge and undercharge protection' and protected with a PCB.
I had bought my original 18350's to use in another battery mod and the ones with the 'pcb' were not yet available. The discussion forum for that other mod said the ones with the pcb are better, but that the original ones I got were probably ok to use since the risk of batteries exploding are more likely when you are using two batteries in series. So I still use my 'yellow' ones if I don't have any of my 'blue' ones charged and available.
The 18350 comes WITH the 3.7v extended cup and it can be charged in the charger that comes WITH the Indulgence itself.
In addition to the single-battery charger that came with my Indulgence I have two other chargers that will charge two batteries at a time. One is a Trustfire TR-001 charger and I can charge two of the 18350's at the same time (or a 18350 and a different battery at the same time). My other one is called a TL-100 (and is also sold under another generic name), but that can only charge a single 18350 because the diameter is a little bigger than the diameter of some other batteries like the 3.7v 16340, so the 18350 is too 'fat' to let you put two of them in the TL100.
Other people I know have that Ultrafire 138 charger shown on that ebay site and they say it will hold two 18350 batteries at a time.