They are horizontal, but from the ones I've taken apart, it's the horizontal type that isn't seated at the very base like Kanger's and Volt's. They're horizontal coils positioned in the middle of the filler section. There are probably benefits and negatives to this design, I guess (equal distribution at both ends of the carto.. on the other hand, the kanger bottom coils aren't touching any filler material at the bottom, so that might have benefits too).