Cartomizers - I want to see light through that center air channel. After I add juice, I tilt the open end down into a tissue (or the sink, or the ground outside) and puff into the threaded end to clear the center channel. If it is not clear then that juice may end up on your battery or in your mouth.
BTW
3-piece ecig is battery + atomizer aka atty + cartridge aka cart
2 piece ecig is battery + cartomizer
cartomizer is from cart+atomizer because it is like a combined cart and atomizer