Checked their site again and it clearly states that the booster containnsv10 ml of the flavour concentrate used in the eliquid. Based on the feedback you should therefore be able to use that to make another +- 100 mls of juice if you use the 7.5% suggested mix rate from their site. It is the same as their single flavour concentrates, that is the part that draws me as it really cuts down the actual cost of the juice. If that is si I would not hesitate to keep buying if it is good as it will be good value.