Pretty much all vape pens follow a standard fitment for the atomizer, which is the part that matters. It's also like the cheapest part. It doesn't really matter what you get because of that, just pick one up at your local smoke shop (if you're 18) or one online. If you're unhappy with it you can buy a new tank/atty for like $10. The only difference between them is the battery size / life and high end ones allow you to adjust voltage to get a stronger/weaker hit.