hat little circular indentation on the side of plastic milk jugs? It’s not a random design flaw, a branding gimmick, or leftover space from the molding process. It’s a clever engineering feature with a very practical purpose—and it has nothing to do with measuring milk or making pouring easier (despite popular myths).Dairy & Eggs
✅ The Real Reason: It’s a “Vacuum Relief” Panel
The dent—technically called a “vacuum panel” or “flex panel”—is designed to compensate for air pressure changes inside the jug, especially as the milk cools or as you pour.
Here’s how it works:
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