As Pete said, the extension cap for the 18650 battery matches in finish perfectly! Unless you bring the ProVari up very close, you'd never notice that it's there. If you look closely, you can see a hairline gap, where the extension cap ends. But again, I'm talking "hairline"... and the finish and material of the extension matches the finish of the ProVari perfectly!
I'd respectfully disagree here, with Pete.
I received my ProVari two days ago, at 5pm. Slapped an 18490 into the ProVari (as others have mentioned, the batteries arrived fully charged), and started vapping away.
At 1am... the ProVari died. Right around 8 hours of pretty heavy vapping, and changing settings and just using the device!
Next day, awoke at 8am. By 3:30pm, using the 18490's, ProVari again died. This time, it was 7.5 hours. So I was able to get very close to eight hours of steady usage from the shorter batteries. Not bad life at ALL, for the shorter batteries!
I'm now trying the 18650's.
I haven't drained the 18650's yet, but I'd guess if they are 1600 mah, and the shorter ones are 1100 mah, I can expect about 50% longer battery life, or 12 hours. Feel free to correct me, if I'm wrong in my calculation, or if others that have used the ProV with the larger batteries have gotten significantly different times.
I already had 2 18650's, for my Ali'i, plus a charger for them. For me, personally, spending the nominal amount for the extension cap gives me the option to use the 18650's if I know I'll be gone all day, or have to carry a 2nd battery with me.
The extra half inch IS noticable, but again... choice is having to bring and carry around a 2nd battery, or just have a slightly longer, slightly heavier device! The extension is almost like having two different devices, as it does give the ProVari a different feel to it, while providing significantly longer battery life!
