They have a refillable tank (which is easily replaceable) and lots of different batteries which will fit. After a while you will realize the limitations of the eGo and will probably want to spend a bit more money on something with a better build quality/features, but to start off, definitely check out the eGo-T.
Yeah, an eGo-T or similar is a good bet for a starter hookah pen: http://www.hookahcompany.com/e-cigarette...
As far as flavors, my favorite e-liquid brand right now is Austin's E-Cig (because I like that they strictly use vegetable glycerin as the base for their e-liquid): http://www.hookahcompany.com/austins-e-c...
But I also enjoy some other brands - Starbuzz makes good e-juice, as well as Tsunami.
Hope that helps.
Im looking to buy a hookah pen. Can someone fill me in on what good brands/pens to buy? And also flavors? I wanna get one like an E Cig to where I can refill it. Just dont know where to get a good one.