optical illusion cup / cup

It is very common for Chinese people to drink alcohol excessively due to the Chinese drinkingculture.
Most people drink alcohol reluctantly upon certain circumstances as a way to show respect and being polite.
This cup is intended to contain white wine or Baijiu,made of transparent glass. The design of the diagonal
stripes can cause optical illusion. Drinkers can choose pour third or two-thirds of the capacity of the cup to
drink less. And people cannot tell howmuch liquor the cup has from the outside by their eyes.