Everything was fine, we just managed to fill only 11 balloons instead of 30. I think gas was leaking from somewhere as we were filling them, that's why it emptied so quickly. I don't think we did anything wrong but I don't know what the problem was. Also, the instructions on the box were different from those in the leaflet. Luckily, we watched a video before doing anything. Anyway, it was very easy to fill the balloons.

It does its job! I tried it both with a booster and on its own... so I can confidently say that if you don't get a booster, it's a waste of money, because they will last only 4-5 hours, not more, and after 2 hours they gradually lose height! With the booster, around 14-16 hours. But I don't think the product (bottle) I bought is to blame, but rather that this is how long helium lasts generally without a booster, so I am very satisfied with the product and it is easy to use!