4 and 4.5 ohm cartomizers, or lower if they wanted a warmer vape.
Keep in mind the clearomizers and carto tanks have only been around a couple of years. Back when the 6v and 7.2v mods came out all we had was cartomizers at around 3 ohms and they left a lot to be desired! Then someone stacked two 123A batteries in an 18650 mod and said "Hey, this ain't half bad!" Then it went on from there.
