When I was thinking about quitting smoking, my friend bought me the Fin Deluxe kit from Wal-Mart. Since we don't have any B&M stores in the area, we figured I'd always have the convenience of restocking supplies if it's found at WalMart. I started out buying Fin's pre filled cartos...that got pricey, and almost to the point of being more expensive than smoking (2 packs/per carto? NO). I then tried Blu's cartos since they had flavors, but out of the box of 5, usually 2 were duds. And then I found ECF- through this forum I learned about Fin's 510 threading and about cartos and juice. Thanks to this forum, it's been 5 months since I quit analogs. And I have definitely saved lots of $$. So the batteries are inexpensive enough for me to have multiples, with multiple chargers. One day I may upgrade, but for now I am happy with the product and the convenience.