Why are the vials 50ml in a 70ml bottle?
This format, known as "Shake and Vape," allows manufacturers to navigate the ban on selling nicotine-containing bottles larger than 10 ml. By leaving 20 ml of empty space in a 70 ml bottle containing 50 ml of nicotine-free liquid, the manufacturer provides the necessary room for you to add your own nicotine boosters directly into the bottle.
It is a legal and practical workaround: you get a cost-effective large format while complying with the TPD law that limits nicotine containers to small vials. If you add one booster, you get 60 ml of juice; if you add two, you fill the bottle to 70 ml. It is a bit like a cooking recipe where the dish and main ingredients are provided, and you just have to adjust the salt—or rather, the nicotine—to your liking.