I love the CE2...
The core and wicks in these things can last for a very long time.
If you want it to be leak proof and pocket friendly, get the metal ones. These will come apart for cleaning but not as easily as the clear ones. I just dedicate one to a particular juice and use it for weeks till it finally dies.
You will want a syringe or needle tip bottle to fill them.
For a regular 510 battery you can use any of them. 2.4ohm ones will be warmer...the 3ohm ones will be cooler. As a point of reference...standard 510 atties usually run around 2.5ohms. The coils in these are closer to your mouth...so any of them should be nice on your battery.
If you really want the clear ones...the advantage to these besides being able to see the juice level is that they come apart easy for cleaning them out and loading with a new flavor. You can pick up a hand full of BD brand 3ml syringes at the WalMart phramacy and the tubes are the perfect size to replace cracked clearo sleeves. Just cut the ends off the syringe and push it on
They'll usually give you a hand full of these for a buck (and they come in handy for all sorts of projects around the house). The numbers will rub right off the syringe if you like.
The disadvantage of the clear ones are: The ends will crack over time and can leak. A few juices out there are known to eat the plastic from the inside out. Cinnamon and strong apple flavors among them.
At normal voltages I would imagine you can use them straight from the box and not have to mod a thing unless you have some REALLY thick juices. If you do run across one that doesn't wick fast enough, simply lift the lower-most silicon ring at each end of the coil so the wicks have a little more room to breathe. It's that easy. Some folks just pull that ring out all together if they don't intend to pocket the carto (small bits of juice can leak through the wick slots if you totally remove the bottom ring).
The benifit is...they taste very very very close to dripping.
Long lasting carto........out of about 8 packs...I've only ever gotten one dead one, and I was able to repair it with a bit of wire stuffed in the end (it was a little too short to contact the battery). I still have some in rotatation that are over a month and half old. One or two don't wick very well anymore, but I can still use them as drippers or fill them and tilt in a pinch.
Optionally, you can reset the CE2 in a large syringe or pill bottle to create a super tank. Or even buy them premade.
In summary:
The cores in these last forever...worth every penny I think, they've even outlast some of my $11 each custom atomizers! The clear sleeves are garbage...if you really want clear ones...make your own tubes from syringes
