I use these every day, I usually go through about 2 fully loaded ones a day, and it's cool to load several up and take 'em to work with you so you can swap cartos on the fly in like 10 seconds with no fuss/muss. I love carrying about 4-5 around, they are SO clean and easy to swap out you can vape different flavor juices w/o any mess whatsoever, completely plug-n-play once filled.
I use the clear ones and fill with the syringe method, it is very easy and I refill the ones I vaped that day when I get home each night. Once a juice goes in, that's all that goes in that one unless I thoroughly clean it out and start over.
I really prefer the clear ones so I can easily see what's going on inside...when vaping, I can see when it's about ready for a refill, and when filling, I can see exactly how much is needed and where to place the syringe to fill in all the dead spots.
The vaping experience with these for me has made a world of difference, they have allowed me to stop puttering about with vape equipment and just get on with it and enjoy it, since there's literally almost no maintenance besides refilling them, which takes maybe 2-3 minutes, and they give me a vape that is completely enjoyable with no negatives.
I mean, when I smoked analogs I didn't make a hobby out of it, I made sure I had enough and went about my business.
The vaping learning curve/obsession has finally leveled out a lot because of using these, they have gotten me just about back to where I was with analogs, ...just load up and go about your business and enjoy whenever you please, there's no futzing with juice running all over the place and on your fingers and loading this and dripping that...it's just so straightforward and easy and painless, I couldn't ask for much more.
Love these things!