I purchased a bottle of menthol e-juice, 24mg of Nicotine in 5ml bottle. If 20 drops is 1 ml then the bottle would hold 1oo drops. That would work out to ,24mg of Nicotine per drop. If I refilled my cartridge with 4 drops the amount of Nicotine would be.96 a cigarette is about 1.1 mg of Nict. So I would have roughly the amount of Nicotiine in 1 cig in my cartridge. When I bought prefilled the manufacturer said each prefilled cart was about a pack of cigs (20). By my calculations this is way off. Does this sound right? If the Math is solid then this is a real ripoff.