KirbyG's Diner - How old were you when you learned the indented circle on a milk jug will pop out when the milk is spoiled? | Facebook
![What is this concave circle on the side of my milk jug? There's only one, there isn't an opposite shape on the other side.. : r/whatisthisthing What is this concave circle on the side of my milk jug? There's only one, there isn't an opposite shape on the other side.. : r/whatisthisthing](https://preview.redd.it/68vlrosn8nb21.jpg?auto=webp&s=071648be0281f4be4323666fab849beb2bd1f866)
What is this concave circle on the side of my milk jug? There's only one, there isn't an opposite shape on the other side.. : r/whatisthisthing
![What is this concave circle on the side of my milk jug? There's only one, there isn't an opposite shape on the other side.. : r/whatisthisthing What is this concave circle on the side of my milk jug? There's only one, there isn't an opposite shape on the other side.. : r/whatisthisthing](https://i.imgur.com/cloCD39.jpg)