Im fairly new to vaping been at it for about a month now and love it. I'm looking to upgrade from my smoktech vv to a mod and want the zmax telescopic. My question is what's the difference in the flat top and the round top version? I'll be using smoktech aro 2 tanks and a kanger pro 2 tank so what is the best ohm coils to use? Sorry for the questions but i want to buy the right model and have it perform well. Also how long do the batteries last in these mods? Thanks