E-liquids are sold in larger bottles that are filled to 80% capacity by participating manufacturers to allow enough room in the bottle for vapers to add one or x2 Nic shots containing nicotine. By adding 10ml of 18mg nicotine-shot to every 50ml short-fill e-liquid and then shaking the mix well, this will produce a 60 ml mix of e-liquid containing 0.3% or 3mg nicotine and by adding 2 bottles of 10ml of 18mg nicotine shot every 100ml short-fill e-liquid and then shaking the mix well, this will produce a 120ml mix of e-liquid containing 0.3% or 3mg nicotine.