It is a top coil clearomizer that often comes in eGo kits. Its clear plastic shell allows you to always see how much e-liquid you've got in the tank. It has a screw-in mouthpiece which seals around the atomizer to prevent leakage.
UPDATE: 2018 - this clearomizer, especially its variant with hidden wicks, is still in use and there is a good reason for it. Actually, a couple of them - widely available, favorably priced, compatible with popular eGo and EVOD batteries, easy to use, spends little e-liquid when compared to more advanced tanks - CE4 is the Toyota of clearomizers.
Two CE4s can last for a month without any special attention, if they aren't DOA (dead on arrival) and unless you burn them with too high voltage.
If you are looking to purchase in US, just click the banner below and you'll find a variety of clearomizers.
Make sure you look for Apollo coupon codes. You'll find even bigger discounts there for holidays. Look for them on their rotating banner.
There's another place where you can buy this as well as many other clearomizers - Central Vapors.
Update, In UK - EcigaretteDirect aka Smoker's Angel you can find only Aspires and a variant of CE5 there now. However, CE5 has issues, so I'd stick with Aspires.
It can last up to two weeks if:
Apollo gives two week warranty on its CE4 clearomizer from their eGo Superior Kit. (Link to our review)
This clearomizer goes very well with eGo batteries both functionally and esthetically. That's why this type of clearomizer is often sold with eGo batteries in a kit.
Don't mistake eGo CE4 for TGo CE4. They look similar and both have the same price! (Update 2015 - TGo has somehow fallen by the wayside, it's mostly eGo in the stores today).
A couple of possible reasons
1. You might have started to vape too soon. Allow a couple of minutes for wicks to absorb the liquid thoroughly.
2. You might have started to vape it at too high voltage. I noticed that the best voltage for them is the low one - 3.0 - 4.0V.
3. Everybody manufactures CE4 today. This is both advantage and disadvantage. Take a look at the pic below. I hope you can see the uneven surface in the central circle. Well, my daughter brought one CE4 the central circle of which was totally even - and it didn't work, of course. So, make sure you buy things from a supplier that lets you return DOA items.
An advice is to buy more Ce4-s when you see them offered at a discount.
To avoid confusion, know that there is also a short wick variant. And there are newer versions of this clearomizer that can be taken apart and washed.
We took it apart once just to see what's in there, we washed it and it was never like before. I see people still looking for advice how to dissasemble it and put it back together. Probably because many eGos are still sold in kits with 2 CE4s. Use a screwdriver, unscrew the bottom part and let everything dry thoroughly after you wash it. But if I were you, I'd rather buy CE5 now.
What you see here is called CE4S by its manufacturer and can normally be taken apart. We ordered it from China and it was DOA.
Time to meet Mr. D (my husband) and time for him to jump in because another clearomizer needed resuscitation. (He is one of those engineer types that just won't leave things alone:)
Btw, I tried to see the difference between CE4s and CE5 but I couldn't really. There seems to be more difference between CE5 from various manufacturers than between these two. It's the overall confusion some other reviewers have already talked about. Everything has been developing pretty fast.