Plastic Gallon Containers Why Do Plastic Milk Containers (gallon And Half Gallon) Have Large Round Indents In The Side?

Why do plastic milk containers (gallon and half gallon) have large round indents in the side? - plastic gallon containers

You are in every purchase from big bottle (ie, Michigan, USA), or find milk, orange juice, apple juice, lemonade ...

Scripts in the middle of the cycle of one or both sides, about 3 cm in diameter, but in bottles of very diffent script in depth from zero to one inch. Cross Section: \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ ___ / (surface of the cone with a flat bottom).

I wanted to know the age, and I can not do a good reason, they think - I think, do initailly to the manufacture of the bottle ... but it would be best to add stiffness and does not explain the different depths.

There should be a good answer!