Zigs Electronic Cigarette Cartridge refills provide the water, nicotine and propylene glycol allowing the electronic cigarette to create a very fine vapour that looks like smoke and when inhaled provides a nicotine hit very simular to a conventional cigarette but much safer for the body. None of the other harmful chemicals such as tar, carcinogenic toxins and carbon monoxide are present when using Zigs cartridges with our electronic cigarette. Some cartridges come in four strengths High, Med, Low and Zero nicotine and we recommend a smoker starts with the high nicotine to make the transition to Electronic Cigarettes.