When it works right, the white cap can prevent leaking in any position. However, I believe many of you have E2's with a more shallow groove in the white cap. These do not work near as often as the older ones. To give you an idea, I'll post some images here that have already been shown. These images are of a cutaway E2 that is used for testing. I have it rigged up so that I can see the wick while it is in actual use.
The first image is with the thick white cap from and early E2 installed. Notice that there is a thin brown stain across the ceramic cup near the bottom of the cap.
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Next is two examples. On the left is a filler ring installed. On the right is a thinner white cap with a more shallow groove. Notice the brown stain across the ceramic cup. This is how far down the older cap went. Even if the white cap shown here does not prevent all leaks, it's a lot easier to install after filling or maintenance.
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Here is what the complete cutaway looks like. The left one shows the Release 3.5 filler ring installed. Notice that it goes all the way down to the brown stain. It will prevent most leaks, but not all. On the right is the same thing with sleeves over the cutouts. The cartomizer can be used with them installed, and the liquid level can be seen.
Nice cutting there, doctor. You just gave me an idea. (drumroll.......)
CLEAR CARTOS! Never have to guess how much juice is left in your cartomizer ever again! *
* Propellers extra.
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