yea sorry i pasted the wrong on first, I think the O ring is the insulator for the centre pin and you will short the batt out if its not there, I could be wrong but i dont think so proceed at your peril my friend, there are 2 O rings in there as the pic shows and this will keep the pin central
link for O ring sizes
http://www.e-cigarette-forum.com/forum/gg/196089-ggts-ufs-avs-o-rings-guide.html
link for O ring sizes
http://www.e-cigarette-forum.com/forum/gg/196089-ggts-ufs-avs-o-rings-guide.html
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