hard

We are such little tiny creatures; all of us have different features. One of us in glass is set; One of us you'll find in jet. Another you may see in tin, and the fourth is boxed within. If the fifth you should pursue, it can never fly from you. What are we?
Common Wrong Answers
“Insects”
Insects do have different features and can be found in various environments, but they don't correspond to the specific clues about being found in glass, jet, tin, or boxed.
“Colors”
Colors can be found in various forms and materials, but they do not fit the clues provided in the riddle about the specific containers or the idea of being pursued.
“Letters”
While the correct answer is related to letters, the guess 'letters' is too vague and does not specifically identify the vowels, which are the key focus of the riddle.