In parts of Canada, milk commonly comes in 1.3-liter plastic bags rather than the plastic jugs and aseptic containers common in the U.S. The bags are un-resealable, so you have to snip the corner and place the bag into a pitcher for pouring, which may seem inconvenient and lead some to wonder why these bags exist.

Canadian milk was once packaged in glass bottles, but these became expensive to replace, so a company called DuPont created plastic bags that could store milk in 1967. Canada also switched to the metric system in the 1970s, and plastic bags were easier to convert to metric measurements than hard plastic.

More than a dozen other countries sell bagged milk, and some areas of the US started using them in schools decades ago in the form of the Mini-Sip, a small pouch also made by DuPont. Though many areas have discontinued bagged milk, you can still find the packaging in Ontario, Québec, and the Maritimes.