We sell both the KR808D-1 and 510 cartomizers. Both the prefilled and the blank cartomizers can be refilled easily using several different methods. I'll explaint he pro's and con's of each method.
Now what you will see is the wicking material and a wire (just above the hole in the center) which attaches to the atomizer coil inside the cartridge (see photo above). Inspect the wicking material and if it looks dirty or burnt, discard the cartomizer and use another one.
The best way to fully fill this cartridge is to place the tip of your e-Liquid dropper tip on the side of the cartomizer and let it flow down the inside of the cartridge body and into the wick. Concentrate it to one area until you see the wick material become saturated all around. If you fill all over the top then you may trap air beneath the top and the cartridge won't fill completely. If you overfill the cartomizer, simply place the open end into a papertowel and blow as hard as you can through the battery connection end.
PROS: Easy to do. You can see the fill level. Ability to somewhat inspect the condition of the wicking material. Easier to guard against overfilling if using automatic batteries.
CONS: End cap may break during removal and not be re-usable. A little more work than some people want to do.
The "push" method
Now onto the "push" method or what some people have nicknamed the "condom" method. We recommend this method ONLY when using the cartomizers on a sealed connector battery, typically pushbutton, or a "mod" with a sealed connector and leak proof cap.
You will need one of the rubber cartomizer covers without the center seal to perform this refill method.
While holding the cartridge with the connector end towards the cartomizer cover, insert it carefully and without blocking the hole in the top cap, slowly press the cartomizer down fully into the cover. This forces the e-Liquid up into the cartomizer through the air hole in the battery connector.
Once fully seated into the cover, carefully remove the cover and with a papertowel clean any excess e-Liquid from the cartomizer and especially the battery connector area. You're done!
PROS: Super easy to do and nothing to take apart or break.
CONS: No way to inspect cartomizer internals to check for possible degradation. Automatic batteries at risk for damage from excess e-Liquid in cartomizer connector.
There are a couple more methods in which you can drip liquid one drop at a time into the hole in the battery connector or top cap, but we do not recommend these methods.
I hope this helps anyone curious about how the cartomizer refilling procedure works.
Check out our KR808D-1 blank cartomizers and our 510 blank cartomizers at http://www.VaporKings.com !