Vape juice often comes in nicotine strengths of zero nicotine, 3mg, 6mg, 12mg, and 18mg, although the highest nicotine vape e-liquid may reach 20mg of Nic Salts. These values represent the amount of nicotine in each 1mL of e-liquid and are sometimes expressed as a percentage (such as 1.8% instead of 18mg/mL)