What Are Examples Of Universal Sets In The Real World?

There are infinite sets ...
  - all real numbers
  - all integers
  - all complex numbers
  - all irrational numbers.
There are very large, but not infinite, sets
  - all integrated circuits manufactured by Intel
  - all SKUs sold by Amazon
  - the cataloged stars in the known universe.
There are sets closer to home
  - the students in your class
  - the cookie sheets in your kitchen
  - the clocks in your abode. (A subset of these would be the ones you have to reset for daylight time.)