Here is a question that has boggled me for ages (but not enough to make me do any real research into the topic). Here in Canada we have something called bagged milk. Bagged milk is sold in packages with 3 bags with a total amount of 4 litres of the liquid. The bags have to be placed in a milk bag holder (that probably isn’t its technical name) so the milk can be poured. The illustration below may help with the visualisation:
If there are any other places in the world that milk comes in bags please tell me!!! Maybe I will do some research of this tomorrow.
P.S. We can also buy cartons of milk (like the rest of the world) but most people buy it in the bag form.