If you've grown up watching high school comedies (in the vein of American Pie); you must be well acquainted with the concept of "baptism by the red party cup"!

Well, these lines here designate ideal serving sizes of different types of alcohol.

The bottom line indicates a shot of liquor (ounce), the middle line is for a serving of wine (5 ounces) and the top line shows the right amount of beer that should ideally be poured (at 12 ounces).

What is more amazing is that the company did not plan it that way but somehow, those markings came out to be accurate enough!